How do you prove $sin(pi/2-theta) = cos theta$ ?

Question

2560 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-04-07T16:55:54

Use $sin(a-b)=sin a cos b - cos a sin b$ . Here, $a = pi/2 and b = theta. sin (pi/2)=1 and cos (pi/2)=0$ .

This way, you can prove all similar results, like, for example, $sin(pi-theta)=sin theta$ .

How do you prove sin(pi/2-theta) = cos theta sin(pi/2-theta) = cos theta ?