根号3tan70+根号3tan80-tan70tan80

题目

根号3tan70+根号3tan80-tan70tan80

答案

tan(70+80)=(tan70+tan80)/(1-tan70tan80)=-1/√3
1-tan70tan80=-√3*(tan70+tan80)
√3tan70+√3*tan80-tan70tan80=-1