Question

How do you verify `cos (x - pi/2) = -sinx`?

Answer 1

see below

Explanation:

Use Property: `cos(A-B)=cosAcosB+sinAsinB`

`A=x, B=pi/2`

left Side:`=cos(x-pi/2)=cosxcos(pi/2)+sinxsin(pi/2)`

`=cosx * 0+sinx * (1)`

`=sinx`