1+根号3*tan10度为何等于1,

题目

1+根号3*tan10度为何等于1,
应为：(1+根号3*tan10)*cos40

答案

(1+根号3*tan10)*cos40
=(1+根号3*tan10)*cos40
=(1+根号3sin10/cos10)*cos40
=(cos10+根号3sin10)*cos40/cos10
=2sin(10+30)*cos40/cos10
=sin80/cos10
=sin80/sin80
=1