Question

Given cosx= 4/5 when (3π/2) < x<2π find sin2x

A. 18/24
B -18/25
C.-1/5
D. -24/25

Answer 1

D -24/25

Explanation:

sin(2x) = 2sin(x)cos(x)

cos(x) = ⅘

sin²(x) = 1 - cos²(x) = 1 - (⅘)²

sin²(x) = 9/25

sin(x) = -⅗

(Because 4th quadrant)

sin(2x) = 2(-⅗)(⅘)

= -24/25