Question

化简cos10°/tan20°+根号3sint10°tan70°-2cos40°

Answer 1

cos10°/tan20°+√3sin10°tan70°-2cos40° =cos10°/tan20°+√3sin10°/tan20°-2cos40° =2(1/2cos10°+√3/2sin10°)/tan20°-2cos40° =2(sin30°cos10°+cos30°sin10°)/tan20°-2cos40° =2sin40°/tan20°-2cos40° =4sin20°cos20°/tan20°-2cos40° =4cos20°-2cos40° =4cos20°-2(2cos20°-1) =2