求(sin105°-根号3倍cos105°)(根号3倍15°-sin15°)的值
问题描述：
求(sin105°-根号3倍cos105°)(根号3倍15°-sin15°)的值
答
(sin105°-根号3倍cos105°)(根号3倍15°-sin15°)
=2(1/2sin105-根号3/2cos105)* 2(根号3/2cos15-1/2sin15)
=2(sin30sin105-cos30cos105)* 2(cos30cos15-sin30sin15)
=4(-cos(135))*(cos(45))
=4cos45cos45
=2(cos90+1)
=2