sin²40°+sin²50°+tan²40°tan²50°的值

问题描述:

sin²40°+sin²50°+tan²40°tan²50°的值

sin²40°+sin²50°+tan²40°tan²50°
= sin²40°+cos²40°+tan²40°cot²40°
=1+1
2诱导公式?cosx=sin(90-x)cotx=tan(90-x)