cos150度+sin60度+tan315度=cos(90+60)+sin(60)+tan(45+90+180)按和差公式=cos90`cos60-sin90sin60+sin60+[(tan(45+90)+tan(180)]/(1-tan45+90tan180)……=-1
负二分之根号三
答: cos150度=-√3/2
cos150°=cos(180°-30°)=-cos30°=-√3/2
