化简：
1.sin(-1071)sin99+sin(-171)sin(-261)
2.1+sin(α-2派)sin(派+α)-2cos2(-α) cos2=cos平方 派=那个3.1415926..
3.已知 sin(x+派/6)=1/4
求 sin(5派/6-x)+sin2(派/3-x)的值
谢谢咯
需要详细的解答，或方法
1.sin(-1071)sin99+sin(-171)sin(-261)
=sin(9)*sin(99)+sin(-9)*sin(99)
=sin(9)*sin(99)-sin(9)*sin(99)
=0
2.1+sin(α-2派)sin(派+α)-2cos2(-α)
=1+sina*(-sina)-2(cosa)^2
=1-sina*sina-2(cosa)^2
=-(cosa)^2
3.
sin(5派/喊芦6-x)+sin2(派/3-x)
=sin(派-(5派/6-x))+cos2(派/2-(派/3-x))
=sin(派/6+x)+cos2(派/6+x)
=sin(派/6+x)+1-sin2(派郑弊带/卜核6+x)
=1/4+1-(1/4)^2
=19/16