Question

Solve sint = cos2t, for –4π ≤ t ≤ –2π

Answer 1

-(23/6)π

-(19/6)π

-3π

Explanation:

cos2t=cos^2t-sin^2t => cos^2t=1-sin^2t =>cos2t=1-2sin^2t

sint=1-2sin^2t, if x=sint, thenn we have 2x^2+x-1=0

Here x=0.5, x=-1, as x=sint => sint = -1 solutions for -4π to -2π is t=-3π,

sint = 0.5 solutions for -4π to -2π is t= -(23/6)*π, and t = -(19/6)*π