求cos(30° a)cosa sin(30° a)sina=cos〖(30 a...
求cos(30° a)cosa sin(30° a)sina=cos〖(30 a)-a〗的推导过程
cos(30° a)=cos30°cosa-sin30°sina
sin(30° a)=sin30°cosa cos30°sina
代入左边,cos30°(cosa)^2-sin30°sinacosa sin30°sinacosa cos30°(sina)^2=cos30°=右边
答:详情>>
答:详情>>