csc40度+cot80度
解:csc40°+cot80°=1/sin40°+cos80°/sin80°=1/sin40°+cos80°/(2sin40°cos40°)=(2cos40°+cos80°)/(2sin40°cos40°)=(cos40°+2cos60°cos20°)/sin80°=(cos40°+cos20°)/sin80°=2cos30°cos10°/cos10°=√3.
