sin(-120°)cos(1290°)+cos(-1020°)sin(-1050°)=

sin(-120°)cos(1290°)+cos(-1020°)sin(-1050°)= sin(-1200°)-cos1290°+cos(-120)°+cos(-1020)°-sin(-1050°)+tan855° sin平方120°+cos180°+tan45°-cos平方(-330°)+sin(-210°) sin(10°)+sin(20°)cos(50°)求值 cos^15°-sin^15°= sin(α+30°)-sin(α-30°)/cosα sin^2 30°+cos()=1 计算：sin^67.5°-cos^67.5度 sin²15° 把sin变成带cos的 Cos(180°+α)*sin（α+360°)/sin(-α-180°)*cos(-180°-α) sin(33°-x)cos(27°+x)+cos(33°-x)sin(27°+x) sin(70° a)cos(10° a)-cos(70° a)sin(170°-a) sin(a+45°)sin(a+15°)+cos(a+45°)cos(a+15°) cos(α+30°)cosα+sin(α+30°)sinα等于? sin(α+30°)cosα+cos(α+30°)sinα= 为什么sin(90°+α)=cosα ,cos(90°+α)=-sinα 利用和差角公式化简 (2)sin(π/3+α)+sin(π/3-α)(2)sin(π/3+α)+sin(π/3-α)(3)cos(π/4+α)-cos(π/4-α)(4)cos(60°+α)+cos(60°-α)(5)sin(α-β)cosβ+cos(α-β)sinβ(6)cos(α+β)cosβ+sin(α+β)sinβ sin(-150°)cos(-210°)cos(-420°)/cos(-600°)sin(-1050°)化简求值。