Find sin θ/2 cos θ/2 and tan θ/2 cosθ=-3/5 for π/2<θ<π

Answer 1

cosine is negative in quadrants 2 and 3; however, the domain restriction is quadrant 2.

inverse_cosine(3/5) = 53.1301023541559787013144387440907.....

so the angle is T=126.1301023541559787013144387440907.....

sin(T/2) = 0.891521391200678946754170016932812....

cos(T/2) = 0.45297859665949651346411821461108...

tan(T/2) = 1.9681313814277941809214122842582....