已知sina/2-cosa/2=-根号5/5,求tan(2a-π/4)已知sina/2-cosa/2=-根号5/5,且450

问题描述:

已知sina/2-cosa/2=-根号5/5,求tan(2a-π/4)
已知sina/2-cosa/2=-根号5/5,且450

(sina/2-cosa/2)^2=(-根号5/5)^2
sina=4/5,tanatana=-4/3
tan2a=2tana/(1-tan^2a)=24/7
tan(2a-π/4)
=(tan2a-tanπ/4)/(1+tan2a*tanπ/4)
=17/31