Question

If `cosa=m`, what is `sin(a-pi/2)`?

Answer 1

`sin(a-pi/2)=-m`

Explanation:

We can use two formulas here. One `sin(-A)=-sinA` and `sin(pi/2-A)=cosA`

Hence `sin(a-pi/2)=sin(-(pi/2-a))`

= `-sin(pi/2-a)=-cosa=-m`