已知tana=2,则2sin^2+1/sin2a=

问题描述:

已知tana=2,则2sin^2+1/sin2a=

2sin^2a+1/sin2a
=(2sin^2a+sin^2a+cos^2a)/2sinacosa 分子分母同时除以cos^2a
=(3tan^2a+1)/2tana 代入tana=2
=13/4