计算tan70°+tan80°—根号3/3tan70°tan80°的值
问题描述：
计算tan70°+tan80°—根号3/3tan70°tan80°的值
答
tan150=-√3/3=tan(70+80)=(tan70+tan80)/(1-tan70tan80)
tan70+tan80=(-√3/3)(1-tan70tan80)
tan70+tan80=-√3/3+√3/3tan70tan80
所以tan70+tan80-√3/3tan70tan80=-√3/3