cos20°+cos100°+cos140°=?
求cos20°cos10
sin100°cos 110° +cos100°sin110°
求值:cos20°sin20°
计算cos20°cos40°cos80°=多少
计算cos20°cos40°cos80°
1/cos20°-根号3/sin20°
化简:sin50º(1+√3tan10°)-cos20°/cos80°√(1-cos20°)
化简sin20°cos40°+cos20°sin40°=______.
计算:sin10°cos20°sin30°cos40°=______.
cos20°cos10°+sin10°sin10°
sin40°*(1-sin10°)/[sin10°*(cos20°)^2]
计算:(sin20°-sin40°)÷(cos20°-cos40°)