How do you prove sin(x+(π/2))=cosx?

Using just these formulas.enter image source here

1 Answer
Mar 2, 2018

There are 2 ways:
1. Use trig identity:
sin (a + b) = sin a.cos b + sin b.cos a
In this case
sin (x + pi/2) = sin x.cos (pi/2) + sin (pi/2).cos x.
Because cos (pi/2) = 0; and sin (x/2) = 1, therefor,
#sin (x + pi/2) = cos x#
2. By the unit circle.