sin(10°)+sin(20°)cos(50°)求值

sin(10°)+sin(20°)cos(50°)求值 sin(70° a)cos(10° a)-cos(70° a)sin(170°-a) (cos^2 10°-cos^2 80°)+sin^2 20° sin(α+30°)-sin(α-30°)/cosα sin²15° 把sin变成带cos的 求值:3/(sin^2 20°)-1/(cos^2 20°)+64sin^2 20° cos(25°+x)cos(20°-x)-cos(65°-x)sin(20°-x) 3-cos 20°/2-sin ^2 80°等于 sin^2 80°为什么等于 cos^2 10°? cos^15°-sin^15°= sin^2 30°+cos()=1 计算：sin^67.5°-cos^67.5度 求值：sin(10°+x)cos(50°-x)+sin(50°-x)cos(10°+x) cos(50°+a)·sin(70°-a)+cos(40°-a)·sin(20°+a) 计算：cos(70°+α)sin(170°-α)-sin(70°+α)cos(10°+α) 计算 cos(40° +A)*sin(10°+A)+sin(40°+A)*cos(170°-A) sin cos cos(27°+x)sin(57°+x)-sin(207°+x)sin(327°+x)