Question

How do you verify `Cos(180° - theta) = -cos theta`?

Answer 1

Please see below.

Explanation:

One of the easiest ways could be to use the formula

`cos(A-B)=cosAcosB+sinAsinB`

Hence, `cos(180^o-theta)=cos180^ocostheta+sin180^osintheta`

= `(-1)xxcostheta+0xxsintheta`

= `-costheta`