cos60°+sin210°=______.
cos60°+sin210°=cos60°+sin(180°+30°)=cos60°-sin30°=12-12=0.
故答案为:0
I_______ have watched that movie —it’ll give me horrible dreams.
A.shouldn’t
B.needn’t
C.couldn’t
D.mustn’t
编制装配工艺规程的原则是什么?