Question

How do you simplify `cos(x+pi)`?

Answer 1

See the Explanation.

Explanation:

We use the Formula `: cos(A+B)=cosAcosB-sinAsinB`

Letting, `A=, &, B=pi`, we get,

`cos(x+pi)=cosxcospi-sinxsinpi`

Since, `cospi=-1, and, sinpi=0`,

`cos(x+pi)=-cosx`.