if sine theta=.3416 and theta is in quadrant I what is cos theta/2? Using double angle identities.

Answer 1

cos 2θ = 2cos^2θ - 1, so

cos θ/2 = √((1+cosθ)/2)

since sinθ = .3416, cosθ = .9398

so, cos θ/2 = √((1+.9398)/2) = .9848

check: θ = 19.97°
cos 9.985° = .9848