Question

已知α∈(π/2,π),且sinα=3/5,则sin^2α/2+(sin4αcos2α)/(1+cos4α)的值为多

Answer 1

cosα=-4/5

原式=(1-cosα)/2+(2sin2αcos^22α)/2cos^22α

=(1-cosα)/2+2sinαcosα

=-3/50