Simplifying and expressing preferentially with cosines

### 9.2.24 Simplifying and expressing preferentially with cosines

Any trigonometric function can be written in terms of sines and cosines, and even powers of sines can be turned into powers of cosines by using the identity sin(x)2+cos(x)2=1. The trigcos command performs these substitutions.

- trigcos takes expr, an expression containing trigonometric functions.
- trigsin(expr) returns expr with the trigonometric functions rewritten in terms of sines and cosines, with as many sines as possible transformed to cosines.

#### Example

trigcos(sin(x)^4+cos(x)^2+1)

cos4x−cos2x+2 |  |  |  |  |  |  |  |  |  |