Помогите, пожалуйста, с решением:

sin(-27π/4)*cos(31π/4)

sin(-27π/4)*cos(31π/4)=sin(-24π/4-3π/4)*cos(24π/4+7π/4)=sin(-3π/4)*cos(7π/4)==sin(-3π/4)*cos(6π/4+π/4)=sin(-3π/4)*cos(π/4)=-4/2=-2