### 10.2.23 Simplifying and expressing preferentially with sines

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

- trigsin 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 cosines as possible transformed to sines.

#### Example

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

sin4x−sin2x+2 |  |  |  |  |  |  |  |  |  |