Question

Find sin2A if sinA=1/4 and 0<=A<=(pi/2)

Answer 1

sin A = 1/4
cos² A = 1 - sin² A
cos² A = 1 - 1/16
cos² A = 15/16
cos A = √15 / 4
-------------------------
sin 2 A = 2 sin A cos A
sin 2 A = 2 · 1/4 · √15 / 4
sin 2 A = √15 / 8