Question

How do you simplify `cos(x-pi/2)`?

Answer 1

`sin x`

Explanation:

Consider the identity: `cos(A-B) = cosAcosB + sinAsinB`

In this example: `A=x and B=pi/2`

Therefore: `cos(x-pi/2) = cosxcos(pi/2) + sinxsin(pi/2)`
`cos(x-pi/2) = cosx*0 + sinx * 1 = sinx`