计算:cos(70°+α)sin(170°-α)-sin(70°+α)cos(10°+α)

问题描述:

计算:cos(70°+α)sin(170°-α)-sin(70°+α)cos(10°+α)

sin x = sin (180° - x)所以,sin (170° - a) = sin [180° - (170° - a)]= sin (10° + a)根据方程式,sin(u ±v) = sin u cos v ± cos u sin vsin (10° + a) cos (70° + a) - cos (10° + a) sin (70° + a) =...