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