# The Derivative of tan(2x)

The derivative of tan(2x) is 2sec2(2x)

## How to calculate the derivative of tan(2x)

Note that in this post we will be looking at differentiating tan(2x) which is not the same as differentiating tan2(x). Here is our post dealing with how to differentiate tan^2(x).

The chain rule is useful for finding the derivative of a function which could have been differentiated had it been in x, but it is in the form of another expression which could also be differentiated if it stood on its own.

In this case:

• We know how to differentiate tan(x) (the answer is sec2(x))
• We know how to differentiate 2x (the answer is 2)

This means the chain rule will allow us to differentiate the expression tan(2x).

#### Using the chain rule to find the derivative of tan(2x)

To perform the differentiation tan(2x), the chain rule says we must differentiate the expression as if it were just in terms of x as long as we then multiply that result by the derivative of what the expression is actually in terms of (in this case the derivative of 2x).

Let’s call the function in the argument of tan, g(x), which means the function is in the form of tan(x), except it does not have x as the angle, instead it has another function of x (2x) as the angle

If:

g(x) = 2x

It follows that:

tan(2x) = tan(g(x))

So if the function f(x) = tan(x) and the function g(x) = 2x, then the function tan(2x) can be written as a composite function.

f(x) = tan(x)

f(g(x)) = tan(g(x)) (but g(x) = 2x))

f(g(x)) = tan(2x)

Let’s define this composite function as F(x):

F(x) = f(g(x)) = tan(2x)

We can find the derivative of tan(2x) (F'(x)) by making use of the chain rule.

The Chain Rule:
For two differentiable functions f(x) and g(x)

If F(x) = f(g(x))

Then the derivative of F(x) is F'(x) = f’(g(x)).g’(x)

Now we can just plug f(x) and g(x) into the chain rule. But before we do that, just a quick recap on the derivative of the tan function.

The derivative of tan(x) with respect to x is sec2(x)
The derivative of tan(z) with respect to z is sec2(z)

In a similar way, the derivative of tan(2x) with respect to 2x is sec2(2x).

We will use this fact as part of the chain rule to find the derivative of tan(2x) with respect to x.

How to find the derivative of tan(2x) using the Chain Rule:

Using the chain rule, the derivative of tan(2x) is 2sec2(2x)

Finally, just a note on syntax and notation: tan(2x) is sometimes written in the forms below (with the derivative as per the calculation above). Just be aware that not all of the forms below are mathematically correct.

## The Second Derivative Of tan(2x)

To calculate the second derivative of a function, you just differentiate the first derivative.

From above, we found that the first derivative of tan(2x) = 2sec2(2x). So to find the second derivative of tan(2x), we just need to differentiate 2sec2(2x).

We can use the chain rule to find the derivative of 2sec2(2x) (bearing in mind that the derivative of sec^2(x) is 2sec2(x)tan(x)) and it gives us a result of 8sec2(2x)tan(2x)

The second derivative of tan(2x) is 8sec2(2x)tan(2x)

# The Derivative of cos(2x)

The derivative of cos(2x) is -2sin(2x)

## How to calculate the derivative of cos(2x)

Note that in this post we will be looking at differentiating cos(2x) which is not the same as differentiating cos2(x). Here is our post dealing with how to differentiate cos^2(x).

The chain rule is useful for finding the derivative of a function which could have been differentiated had it been in x, but it is in the form of another expression which could also be differentiated if it stood on its own.

In this case:

• We know how to differentiate cos(x) (the answer is -sin(x))
• We know how to differentiate 2x (the answer is 2)

This means the chain rule will allow us to differentiate the expression cos(2x).

#### Using the chain rule to find the derivative of cos(2x)

To perform the differentiation cos(2x), the chain rule says we must differentiate the expression as if it were just in terms of x as long as we then multiply that result by the derivative of what the expression is actually in terms of (in this case the derivative of 2x).

Let’s call the function in the argument of cos, g(x), which means the function is in the form of cos(x), except it does not have x as the angle, instead it has another function of x (2x) as the angle

If:

g(x) = 2x

It follows that:

cos(2x) = cos(g(x))

So if the function f(x) = cos(x) and the function g(x) = 2x, then the function cos(2x) can be written as a composite function.

f(x) = cos(x)

f(g(x)) = cos(g(x)) (but g(x) = 2x))

f(g(x)) = cos(2x)

Let’s define this composite function as F(x):

F(x) = f(g(x)) = cos(2x)

We can find the derivative of cos(2x) (F'(x)) by making use of the chain rule.

The Chain Rule:
For two differentiable functions f(x) and g(x)

If F(x) = f(g(x))

Then the derivative of F(x) is F'(x) = f’(g(x)).g’(x)

Now we can just plug f(x) and g(x) into the chain rule. But before we do that, just a quick recap on the derivative of the cos function.

The derivative of cos(x) with respect to x is -sin(x)
The derivative of cos(z) with respect to z is -sin(z)

In a similar way, the derivative of cos(2x) with respect to 2x is -sin(2x).

We will use this fact as part of the chain rule to find the derivative of cos(2x) with respect to x.

How to find the derivative of cos(2x) using the Chain Rule:

Using the chain rule, the derivative of cos(2x) is -2sin(2x)

Finally, just a note on syntax and notation: cos(2x) is sometimes written in the forms below (with the derivative as per the calculation above). Just be aware that not all of the forms below are mathematically correct.

## The Second Derivative Of cos(2x)

To calculate the second derivative of a function, you just differentiate the first derivative.

From above, we found that the first derivative of cos(2x) = -2sin(2x). So to find the second derivative of cos(2x), we just need to differentiate -2sin(2x)

We can use the chain rule to find the derivative of -2sin(2x) and it gives us a result of -4cos(2x)

The second derivative of cos(2x) is -4cos(2x)

# The Derivative of sin(2x)

The derivative of sin(2x) is 2cos(2x)

## How to calculate the derivative of sin(2x)

Note that in this post we will be looking at differentiating sin(2x) which is not the same as differentiating sin2(x). Here is our post dealing with how to differentiate sin^2(x).

The chain rule is useful for finding the derivative of a function which could have been differentiated had it been in x, but it is in the form of another expression which could also be differentiated if it stood on its own.

In this case:

• We know how to differentiate sin(x) (the answer is cos(x))
• We know how to differentiate 2x (the answer is 2)

This means the chain rule will allow us to differentiate the expression sin(2x).

#### Using the chain rule to find the derivative of sin(2x)

To perform the differentiation sin(2x), the chain rule says we must differentiate the expression as if it were just in terms of x as long as we then multiply that result by the derivative of what the expression is actually in terms of (in this case the derivative of 2x).

Let’s call the function in the argument of sin, g(x), which means the function is in the form of sin(x), except it does not have x as the angle, instead it has another function of x (2x) as the angle.

If:

g(x) = 2x

It follows that:

sin(2x) = sin(g(x))

So if the function f(x) = sin(x) and the function g(x) = 2x, then the function sin(2x) can be written as a composite function.

f(x) = sin(x)

f(g(x)) = sin(g(x)) (but g(x) = 2x))

f(g(x)) = sin(2x)

Let’s define this composite function as F(x):

F(x) = f(g(x)) = sin(2x)

We can find the derivative of sin(2x) (F'(x)) by making use of the chain rule.

The Chain Rule:
For two differentiable functions f(x) and g(x)

If F(x) = f(g(x))

Then the derivative of F(x) is F'(x) = f’(g(x)).g’(x)

Now we can just plug f(x) and g(x) into the chain rule. But before we do that, just a quick recap on the derivative of the sin function.

The derivative of sin(x) with respect to x is cos(x)
The derivative of sin(z) with respect to z is cos(z)

In a similar way, the derivative of sin(2x) with respect to 2x is cos(2x).

We will use this fact as part of the chain rule to find the derivative of sin(2x) with respect to x.

How to find the derivative of sin(2x) using the Chain Rule:

Using the chain rule, the derivative of sin(2x) is 2cos(2x)

Interestingly, the first derivative of sin(2x) is equal to the second derivative of sin2(x). The reason for this is because the derivative of sin2(x) is equal to sin(2x), which is what we just differentiated.

Finally, just a note on syntax and notation: sin(2x) is sometimes written in the forms below (with the derivative as per the calculation above). Just be aware that not all of the forms below are mathematically correct.

## The Second Derivative Of sin(2x)

To calculate the second derivative of a function, you just differentiate the first derivative.

From above, we found that the first derivative of sin(2x) = 2cos(2x). So to find the second derivative of sin(2x), we just need to differentiate 2cos(2x)

We can use the chain rule to find the derivative of 2cos(2x) and it gives us a result of -4sin(2x)

The second derivative of sin(2x) is -4sin(2x)

# The Derivative of cot^2x

The derivative of cot^2x is -2.csc^2(x).cot(x)

## How to calculate the derivative of cot^2x

There are two methods that can be used for calculating the derivative of cot^2x.

The first method is by using the product rule for derivatives (since cot2(x) can be written as cot(x).cot(x)).

The second method is by using the chain rule for differentiation.

### Finding the derivative of cot^2x using the product rule

The product rule for differentiation states that the derivative of f(x).g(x) is f’(x)g(x) + f(x).g’(x)

The Product Rule:
For two differentiable functions f(x) and g(x)

If F(x) = f(x).g(x)

Then the derivative of F(x) is F'(x) = f’(x)g(x) + f(x)g'(x)

First, let F(x) = cot2(x)

Then remember that cot2(x) is equal to cot(x).cot(x)

So F(x) = cot(x)cot(x)

By setting f(x) and g(x) as cot(x) means that F(x) = f(x).g(x) and we can apply the product rule to find F'(x)

Using the product rule, the derivative of cot^2x is -2csc2(x)cot(x)

### Finding the derivative of cot^2x using the chain rule

The chain rule is useful for finding the derivative of a function which could have been differentiated had it been in x, but it is in the form of another expression which could also be differentiated if it stood on its own.

In this case:

• We know how to differentiate cot(x) (the answer is -csc2(x))
• We know how to differentiate x2 (the answer is 2x)

This means the chain rule will allow us to perform the differentiation of the expression cot^2x.

#### Using the chain rule to find the derivative of cot^2x

Although the expression cot2x contains no parenthesis, we can still view it as a composite function (a function of a function).

We can write cot2x as (cot(x))2.

Now the function is in the form of x2, except it does not have x as the base, instead it has another function of x (cot(x)) as the base.

Let’s call the function of the base g(x), which means:

g(x) = cot(x)

From this it follows that:

(cot(x))2 = g(x)2

So if the function f(x) = x2 and the function g(x) = cot(x), then the function (cot(x))2 can be written as a composite function.

f(x) = x2

f(g(x)) = g(x)2 (but g(x) = cot(x))

f(g(x)) = (cot(x))2

Let’s define this composite function as F(x):

F(x) = f(g(x)) = (cot(x))2

We can find the derivative of cot^2x (F'(x)) by making use of the chain rule.

The Chain Rule:
For two differentiable functions f(x) and g(x)

If F(x) = f(g(x))

Then the derivative of F(x) is F'(x) = f’(g(x)).g’(x)

Now we can just plug f(x) and g(x) into the chain rule.

How to find the derivative of cot^2x using the Chain Rule:

Using the chain rule, the derivative of cot^2x is -2.csc2(x)cot(x)

Finally, just a note on syntax and notation:cot^2x is sometimes written in the forms below (with the derivative as per the calculations above). Just be aware that not all of the forms below are mathematically correct.

## The Second Derivative Of cot^2x

To calculate the second derivative of a function, differentiate the first derivative.

From above, we found that the first derivative of cot^2x = -2csc2(x)cot(x). So to find the second derivative of cot^2x, we need to differentiate -2csc2(x)cot(x).

We can use the product and chain rules, and then simplify to find the derivative of -2csc2(x)cot(x) is 4csc2(x)cot2(x) + 2csc4(x)

The second derivative of cot^2x is 4csc2(x)cot2(x) + 2csc4(x)

## Interesting property of the derivative of cot^2x

It is interesting to note that the derivative of cot2x is equal to the derivative of csc2x.

The derivative of:
> cot2x = -2.csc2(x).cot(x)
> csc2x = -2.csc2(x).cot(x)

# The Derivative of csc^2x

The derivative of csc^2x is -2.csc^2(x).cot(x)

## How to calculate the derivative of csc^2x

Note that in this post we will be looking at differentiating csc2(x) which is not the same as differentiating csc(2x). Here is our post dealing with how to differentiate csc(2x).

There are two methods that can be used for calculating the derivative of cosec^2x.

The first method is by using the product rule for derivatives (since csc2(x) can be written as csc(x).csc(x)).

The second method is by using the chain rule for differentiation.

### Finding the derivative of csc^2x using the product rule

The product rule for differentiation states that the derivative of f(x).g(x) is f’(x)g(x) + f(x).g’(x)

The Product Rule:
For two differentiable functions f(x) and g(x)

If F(x) = f(x).g(x)

Then the derivative of F(x) is F'(x) = f’(x)g(x) + f(x)g'(x)

First, let F(x) = csc2(x)

Then remember that csc2(x) is equal to csc(x).csc(x)

So F(x) = csc(x)csc(x)

By setting f(x) and g(x) as csc(x) means that F(x) = f(x).g(x) and we can apply the product rule to find F'(x)

Using the product rule, the derivative of csc^2x is -2csc^2(x)cot(x)

### Finding the derivative of csc^2x using the chain rule

The chain rule is useful for finding the derivative of a function which could have been differentiated had it been in x, but it is in the form of another expression which could also be differentiated if it stood on its own.

In this case:

• We know how to differentiate csc(x) (the answer is -csc(x)cot(x))
• We know how to differentiate x2 (the answer is 2x)

This means the chain rule will allow us to perform the differentiation of the expression csc^2x.

#### Using the chain rule to find the derivative of csc^2x

Although the expression csc2x contains no parenthesis, we can still view it as a composite function (a function of a function).

We can write csc2x as (csc(x))2.

Now the function is in the form of x2, except it does not have x as the base, instead it has another function of x (csc(x)) as the base.

Let’s call the function of the base g(x), which means:

g(x) = csc(x)

From this it follows that:

csc(x)2 = g(x)2

So if the function f(x) = x2 and the function g(x) = csc(x), then the function (csc(x))2 can be written as a composite function.

f(x) = x2

f(g(x)) = g(x)2 (but g(x) = csc(x))

f(g(x)) = (csc(x))2

Let’s define this composite function as F(x):

F(x) = f(g(x)) = (csc(x))2

We can find the derivative of csc^2x (F'(x)) by making use of the chain rule.

The Chain Rule:
For two differentiable functions f(x) and g(x)

If F(x) = f(g(x))

Then the derivative of F(x) is F'(x) = f’(g(x)).g’(x)

Now we can just plug f(x) and g(x) into the chain rule.

How to find the derivative of csc^2x using the Chain Rule:

Using the chain rule, the derivative of csc^2x is -2.csc^2(x).cot(x)

Finally, just a note on syntax and notation: csc^2x is sometimes written in the forms below (with the derivative as per the calculations above). Just be aware that not all of the forms below are mathematically correct.

## The Second Derivative Of csc^2x

To calculate the second derivative of a function, differentiate the first derivative.

From above, we found that the first derivative of csc^2x = -2csc2(x)cot(x). So to find the second derivative of csc^2x, we need to differentiate -2csc2(x)cot(x).

We can use the product and chain rules, and then simplify to find the derivative of -2csc2(x)cot(x) is 4csc2(x)cot2(x) + 2csc4(x)

The second derivative of csc^2x is 4csc2(x)cot2(x) + 2csc4(x)

## Interesting property of the derivative of csc^2x

It is interesting to note that the derivative of csc2x is equal to the derivative of cot2x.

The derivative of:
> csc2x = -2.csc2(x).cot(x)
> cot2x = -2.csc2(x).cot(x)

# The Derivative of sec^2x

The derivative of sec^2x is 2.sec^2(x).tan(x)

## How to calculate the derivative of sec^2x

There are two methods that can be used for calculating the derivative of sec^2x.

The first method is by using the product rule for derivatives (since sec2(x) can be written as sec(x).sec(x)).

The second method is by using the chain rule for differentiation.

### Finding the derivative of sec^2x using the product rule

The product rule for differentiation states that the derivative of f(x).g(x) is f’(x)g(x) + f(x).g’(x)

The Product Rule:
For two differentiable functions f(x) and g(x)

If F(x) = f(x).g(x)

Then the derivative of F(x) is F'(x) = f’(x)g(x) + f(x)g'(x)

First, let F(x) = sec2(x)

Then remember that sec2(x) is equal to sec(x).sec(x)

So F(x) = sec(x)sec(x)

By setting f(x) and g(x) as sec(x) means that F(x) = f(x).g(x) and we can apply the product rule to find F'(x)

Using the product rule, the derivative of sec^2x is 2sec^2(x)tan(x)

### Finding the derivative of sec^2x using the chain rule

The chain rule is useful for finding the derivative of a function which could have been differentiated had it been in x, but it is in the form of another expression which could also be differentiated if it stood on its own.

In this case:

• We know how to differentiate sec(x) (the answer is sec(x)tan(x))
• We know how to differentiate x2 (the answer is 2x)

This means the chain rule will allow us to perform the differentiation of the expression sec^2x.

#### Using the chain rule to find the derivative of sec^2x

Although the expression sec2x contains no parenthesis, we can still view it as a composite function (a function of a function).

We can write sec2x as (sec(x))2.

Now the function is in the form of x2, except it does not have x as the base, instead it has another function of x (sec(x)) as the base.

Let’s call the function of the base g(x), which means:

g(x) = sec(x)

From this it follows that:

sec(x)2 = g(x)2

So if the function f(x) = x2 and the function g(x) = sec(x), then the function (sec(x))2 can be written as a composite function.

f(x) = x2

f(g(x)) = g(x)2 (but g(x) = sec(x))

f(g(x)) = (sec(x))2

Let’s define this composite function as F(x):

F(x) = f(g(x)) = (sec(x))2

We can find the derivative of sec^2x (F'(x)) by making use of the chain rule.

The Chain Rule:
For two differentiable functions f(x) and g(x)

If F(x) = f(g(x))

Then the derivative of F(x) is F'(x) = f’(g(x)).g’(x)

Now we can just plug f(x) and g(x) into the chain rule.

How to find the derivative of sec^2x using the Chain Rule:

Using the chain rule, the derivative of sec^2x is 2.sec^2(x).tan(x)

Finally, just a note on syntax and notation: sec^2x is sometimes written in the forms below (with the derivative as per the calculations above). Just be aware that not all of the forms below are mathematically correct.

## The Second Derivative Of sec^2x

To calculate the second derivative of a function, differentiate the first derivative.

From above, we found that the first derivative of sec^2x = 2sec2(x)tan(x). So to find the second derivative of sec^2x, we need to differentiate 2sec2(x)tan(x).

We can use the product and chain rules, and then simplify to find the derivative of 2sec2(x)tan(x) is 4sec2(x)tan2(x) + 2sec4(x)

The second derivative of sec^2x is 4sec2(x)tan2(x) + 2sec4(x)

## Interesting property of the derivative of sec^2x

It is interesting to note that the derivative of sec2(x) is equal to the derivative of tan2(x).

The derivative of:
> sec2x = 2.sec2(x).tan(x)
> tan2x = 2.sec2(x).tan(x)

# The Derivative of tan^2x

The derivative of tan^2x is 2.tan(x).sec^2(x)

## How to calculate the derivative of tan^2x

Note that in this post we will be looking at differentiating tan2(x) which is not the same as differentiating tan(2x). Here is our post dealing with how to differentiate tan(2x).

There are two methods that can be used for calculating the derivative of tan^2x.

The first method is by using the product rule for derivatives (since tan2(x) can be written as tan(x).tan(x)).

The second method is by using the chain rule for differentiation.

### Finding the derivative of tan^2x using the product rule

The product rule for differentiation states that the derivative of f(x).g(x) is f’(x)g(x) + f(x).g’(x)

The Product Rule:
For two differentiable functions f(x) and g(x)

If F(x) = f(x).g(x)

Then the derivative of F(x) is F'(x) = f’(x)g(x) + f(x)g'(x)

First, let F(x) = tan2(x)

Then remember that tan2(x) is equal to tan(x).tan(x)

So F(x) = tan(x)tan(x)

By setting f(x) and g(x) as tan(x) means that F(x) = f(x).g(x) and we can apply the product rule to find F'(x)

Using the product rule, the derivative of tan^2x is 2tan(x)sec2(x)

### Finding the derivative of tan^2x using the chain rule

The chain rule is useful for finding the derivative of a function which could have been differentiated had it been in x, but it is in the form of another expression which could also be differentiated if it stood on its own.

In this case:

• We know how to differentiate tan(x) (the answer is sec2(x))
• We know how to differentiate x2 (the answer is 2x)

This means the chain rule will allow us to perform the differentiation of the expression tan^2x.

#### Using the chain rule to find the derivative of tan^2x

Although the expression tan2x contains no parenthesis, we can still view it as a composite function (a function of a function).

We can write tan2x as (tan(x))2.

Now the function is in the form of x2, except it does not have x as the base, instead it has another function of x (tan(x)) as the base.

Let’s call the function of the base g(x), which means:

g(x) = tan(x)

From this it follows that:

tan(x)2 = g(x)2

So if the function f(x) = x2 and the function g(x) = tan(x), then the function (tan(x))2 can be written as a composite function.

f(x) = x2

f(g(x)) = g(x)2 (but g(x) = tan(x))

f(g(x)) = (tan(x))2

Let’s define this composite function as F(x):

F(x) = f(g(x)) = (tan(x))2

We can find the derivative of tan^2x (F'(x)) by making use of the chain rule.

The Chain Rule:
For two differentiable functions f(x) and g(x)

If F(x) = f(g(x))

Then the derivative of F(x) is F'(x) = f’(g(x)).g’(x)

Now we can just plug f(x) and g(x) into the chain rule.

How to find the derivative of tan^2x using the Chain Rule:

Using the chain rule, the derivative of tan^2x is 2.tan(x).sec2(x)

Finally, just a note on syntax and notation:tan^2x is sometimes written in the forms below (with the derivative as per the calculations above). Just be aware that not all of the forms below are mathematically correct.

## The Second Derivative Of tan^2x

To calculate the second derivative of a function, differentiate the first derivative.

From above, we found that the first derivative of tan^2x = 2tan(x)sec2(x). So to find the second derivative of tan^2x, we need to differentiate 2tan(x)sec2(x).

We can use the product and chain rules, and then simplify to find the derivative of 2tan(x)sec2(x) is 4sec2(x)tan2(x) + 2sec4(x)

The second derivative of tan^2x is 4sec2(x)tan2(x) + 2sec4(x)

## Interesting property of the derivative of tan^2x

It is interesting to note that the derivative of tan2x is equal to the derivative of sec2x.

The derivative of:
> tan2x = 2.sec2(x).tan(x)
> sec2x = 2.sec2(x).tan(x)

# The Derivative of cos^2x

The derivative of cos^2x is -sin(2x)

## How to calculate the derivative of cos^2x

Note that in this post we will be looking at differentiating cos2(x) which is not the same as differentiating cos(2x). Here is our post dealing with how to differentiate cos(2x).

There are two methods that can be used for calculating the derivative of cos^2x.

The first method is by using the product rule for derivatives (since cos2(x) can be written as cos(x).cos(x)).

The second method is by using the chain rule for differentiation.

### Finding the derivative of cos^2x using the product rule

The product rule for differentiation states that the derivative of f(x).g(x) is f’(x)g(x) + f(x).g’(x)

The Product Rule:
For two differentiable functions f(x) and g(x)

If F(x) = f(x).g(x)

Then the derivative of F(x) is F'(x) = f’(x)g(x) + f(x)g'(x)

First, let F(x) = cos2(x)

Then remember that cos2(x) is equal to cos(x).cos(x)

So F(x) = cos(x)cos(x)

By setting f(x) and g(x) as cos(x) means that F(x) = f(x).g(x) and we can apply the product rule to find F'(x)

Using the product rule, the derivative of cos^2x is -sin(2x)

### Finding the derivative of cos^2x using the chain rule

The chain rule is useful for finding the derivative of a function which could have been differentiated had it been in x, but it is in the form of another expression which could also be differentiated if it stood on its own.

In this case:

• We know how to differentiate cos(x) (the answer is -sin(x))
• We know how to differentiate x2 (the answer is 2x)

This means the chain rule will allow us to perform the differentiation of the expression cos^2x.

#### Using the chain rule to find the derivative of cos^2x

Although the expression cos2x contains no parenthesis, we can still view it as a composite function (a function of a function).

We can write cos2x as (cos(x))2.

Now the function is in the form of x2, except it does not have x as the base, instead it has another function of x (cos(x)) as the base.

Let’s call the function of the base g(x), which means:

g(x) = cos(x)

From this it follows that:

cos(x)2 = g(x)2

So if the function f(x) = x2 and the function g(x) = cos(x), then the function (cos(x))2 can be written as a composite function.

f(x) = x2

f(g(x)) = g(x)2 (but g(x) = cos(x))

f(g(x)) = (cos(x))2

Let’s define this composite function as F(x):

F(x) = f(g(x)) = (cos(x))2

We can find the derivative of cos^2x (F'(x)) by making use of the chain rule.

The Chain Rule:
For two differentiable functions f(x) and g(x)

If F(x) = f(g(x))

Then the derivative of F(x) is F'(x) = f’(g(x)).g’(x)

Now we can just plug f(x) and g(x) into the chain rule.

How to find the derivative of cos^2x using the Chain Rule:

Using the chain rule, the derivative of cos^2x is -sin(2x)

Finally, just a note on syntax and notation: cos^2x is sometimes written in the forms below (with the derivative as per the calculations above). Just be aware that not all of the forms below are mathematically correct.

## The Second Derivative Of cos^2x

To calculate the second derivative of a function, you just differentiate the first derivative.

From above, we found that the first derivative of cos^2x = -sin(2x). So to find the second derivative of cos^2x, we just need to differentiate -sin(2x)

We can use the chain rule to find the derivative of -sin(2x).

We can set g(x) = 2x and f(x) = -sin(x). the F(x) = f(g(x)) = -sin(2x). We can then apply the chain rule to find F'(x).

The chain rules says that the derivative of F(x) is equal to f’(g(x)).g'(x).

f'(g(x)).g'(x)
= -cos(2x).2
= -2cos(2x)

The second derivative of cos^2x is -2cos(2x)

# The Derivative of sin^2x?

The derivative of sin^2x is 2sin(x)cos(x)

## How to calculate the derivative of sin^2x

Note that in this post we will be looking at differentiating sin2(x) which is not the same as differentiating sin(2x). Here is our post dealing with how to differentiate sin(2x).

There are two methods that can be used for calculating the derivative of sin^2x.

The first method is by using the product rule for derivatives (since sin2(x) can be written as sin(x).sin(x)).

The second method is by using the chain rule for differentiation.

### Finding the derivative of sin^2x using the product rule

The product rule for differentiation states that the derivative of f(x).g(x) is f’(x)g(x) + f(x).g’(x)

The Product Rule:
For two differentiable functions f(x) and g(x)

If F(x) = f(x).g(x)

Then the derivative of F(x) is F'(x) = f’(x)g(x) + f(x)g'(x)

First, let F(x) = sin2(x)

Then remember that sin2(x) is equal to sin(x).sin(x)

So F(x) = sin(x)sin(x)

By setting f(x) and g(x) as sin(x) means that F(x) = f(x).g(x) and we can apply the product rule to find F'(x)

Using the product rule, the derivative of sin^2x is 2sin(x)cos(x)

### Finding the derivative of sin^2x using the chain rule

The chain rule is useful for finding the derivative of a function which could have been differentiated had it been in x, but it is in the form of another expression which could also be differentiated if it stood on its own.

In this case:

• We know how to differentiate sin(x) (the answer is cos(x))
• We know how to differentiate x2 (the answer is 2x)

This means the chain rule will allow us to perform the differentiation of the expression sin^2x.

#### Using the chain rule to find the derivative of sin^2x

Although the expression sin2x contains no parenthesis, we can still view it as a composite function (a function of a function).

We can write sin2x as (sin(x))2.

Now the function is in the form of x2, except it does not have x as the base, instead it has another function of x (sin(x)) as the base.

Let’s call the function of the base g(x), which means:

g(x) = sin(x)

From this it follows that:

sin(x)2 = g(x)2

So if the function f(x) = x2 and the function g(x) = sin(x), then the function (sin(x))2 can be written as a composite function.

f(x) = x2

f(g(x)) = g(x)2 (but g(x) = sin(x))

f(g(x)) = (sin(x))2

Let’s define this composite function as F(x):

F(x) = f(g(x)) = (sin(x))2

We can find the derivative of sin^2x (F'(x)) by making use of the chain rule.

The Chain Rule:
For two differentiable functions f(x) and g(x)

If F(x) = f(g(x))

Then the derivative of F(x) is F'(x) = f’(g(x)).g’(x)

Now we can just plug f(x) and g(x) into the chain rule.

How to find the derivative of sin^2x using the Chain Rule:

Using the chain rule, the derivative of sin^2x is 2sin(x)cos(x)

(Note – using the trigonometric identity 2cos(x)sin(x) = sin(2x), the derivative of sin^2x can also be written as sin(2x))

Finally, just a note on syntax and notation: sin^2x is sometimes written in the forms below (with the derivative as per the calculations above). Just be aware that not all of the forms below are mathematically correct.

## The Second Derivative Of sin^2x

To calculate the second derivative of a function, you just differentiate the first derivative.

From above, we found that the first derivative of sin^2x = 2sin(x)cos(x). So to find the second derivative of sin^2x, we just need to differentiate 2sin(x)cos(x)

We can use the product rule to find the derivative of 2sin(x)cos(x).

We can set f(x) = 2sin(x) and g(x) = cos(x) and apply the product rule to find the derivative of f(x).g(x) = 2sin(x)cos(x)

The product rules says that the derivative of f(x).g(x) is equal to f’(x)g(x) + f(x)g’(x).

2cos(x)cos(x) + 2sin(x)(-sin(x))
= 2cos2(x) – 2sin2(x)
= 2(cos2(x) – sin2(x))

Using the trigonometric double angle identity cos(2x) = cos2(x) – sin2(x), we can rewrite this as

= 2cos(2x)

The second derivative of sin^2x is 2cos(2x)

Interestingly, the second derivative of sin2x is equal to the first derivative of sin(2x).