Question

化简求值（1）sin（-1320°）?cos1110°+cos（-1020°）sin750°（2）sin(2π?α)?cos(?π+α)sin(3π?α

化简求值（1）sin（-1320°）?cos1110°+cos（-1020°）sin750°（2）sin(2π?α)?cos(?π+α)sin(3π?α)?cos(π+α)．

Answer 1

（1）原式=sin（-4×360°+120°）?cos（3×360°+30°）+cos（-3×360°+60°）sin（2×360°+30°）
=

3

2

×

3

2

+

1

2

×

1

2

=1；
（2）原式=

sinαcosα

?sinαcosα

=-1．