tan70°*cos10°(1-√3*tan20)的值
问题描述:
tan70°*cos10°(1-√3*tan20)的值
答
tan70×cos10×(√3tan20-1) =tan70×cos10×(tan60×tan20-1) =tan70×cos10×[(sin60×sin20/cos60×cos20)-1] =tan70×cos10×(sin60×sin20-cos60×cos20)/(cos60×cos20) =tan70×cos10×[-cos(60+20)]/(cos60 ...