Question

cos² θ + cos²(π/2 - θ) = 1
prove the identity

Answer 1

can anybody do it?

Answer 2

cos^2(pi/2 -t ) =
[cos(pi/2 -t)]^2 = [cos(pi/2)cos(t) + sin(pi/2)sin(t)]^2 = sin^2(t)

and
cos^2(t) + sin^2(t) = 1
done

Answer 3

good job. Thanks