# Integration using polar coordinates

**Integration using polar coordinates** is a technique for solving integrals using polar coordinates. Sometimes an integral that is complicated in one set or coordinates, such as Cartesian coordinates become very easy or even trivial in polar coordinates.

## Example

Consider the integral

This can be converted into polar coordinated by multiplying by itself, so that

This can be expressed as the double integral,

Now the usefulness of polar coordinates becomes apparent as in polar coordinates, . The bounds mean the integral is over the entire x-y plane, so varies from to and from to . To convert the differentials, we must multiply by the Jacobian, to get

This can be integrated by separating the integral. The integral gives and the integral gives . This means the initial integral, is .

## Other methods of integration

The primary methods of integration include:

- Integration by parts
- Integration using polar coordinates
- Multiple integration
- Residue calculus (for definite integrals)
- Method of simultaneous convolutions
- Mellin transforms
- Inflation-restriction sequences