计算sin420 cos750+sin(-330)cos(-660)

题目

计算sin420 cos750+sin(-330)cos(-660)
每个数上有小圆,也就是度!急

答案

sin420cos750+sin(-330)cos(-660)
=sin(360+60)cos(2x360+30)+sin(360-330)cos(2x360-660)
=sin60cos30+sin30cos60
=sin(60+30)
=1