When the integrand is primarily or exclusively based on trigonometric functions, the following techniques are useful.

## Contents

### Powers of Sine and CosineEdit

We will give a general method to solve generally integrands of the form . First let us work through an example.

Notice that the integrand contains an odd power of cos. So rewrite it as

We can solve this by making the substitution so . Then we can write the whole integrand in terms of by using the identity

- .

So

This method works whenever there is an odd power of sine or cosine.

To evaluate when

eitheror isodd.

- If is odd substitute and use the identity .
- If is odd substitute and use the identity .

#### ExampleEdit

Find .

As there is an odd power of we let so . Notice that when we have and when we have .

When both and are even things get a little more complicated.

To evaluate when both and are

even.

Use the identities and .

#### ExampleEdit

Find .

As and we have

and expanding, the integrand becomes

Using the multiple angle identities

then we obtain on evaluating

### Powers of Tan and SecantEdit

To evaluate .

- If is even and then substitute and use the identity .
- If and are both odd then substitute and use the identity .
- If is odd and is even then use the identity and apply a reduction formula to integrate , using the examples below to integrate when .

#### Example 1Edit

Find .

There is an even power of . Substituting gives so

#### Example 2Edit

Find .

Let so . Then

#### Example 3Edit

Find .

The trick to do this is to multiply and divide by the same thing like this:

Making the substitution so ,

### More trigonometric combinationsEdit

For the integrals or or use the identities

#### Example 1Edit

Find .

We can use the fact that , so

Now use the oddness property of to simplify

And now we can integrate

#### Example 2Edit

Find: .

Using the identities

Then