A属于(0,π),满足2sin^2a=cos2a-sin2a,求tana

问题描述:

A属于(0,π),满足2sin^2a=cos2a-sin2a,求tana

2sin^2a=cos2a-sin2a2sin²a=cos²a-sin²a-2sinacosa两边同时处以cos²a得2tan²a=1-tan²a-2tana3tan²a+2tana-1=0(3tana-1)(tana+1)=0得 tana=1/3 或 tana=-1因为 a∈(0,π)所以 t...