已知cos(x - π/4)=根号二/10 ,x∈(π/2 ,3π/4),则tanx=_____

问题描述:

已知cos(x - π/4)=根号二/10 ,x∈(π/2 ,3π/4),则tanx=_____

sinx=sin[(x-π/4)+π/4]=sin(x-π/4)cos(π/4)+cos(x-π/4)sinx=4/5
∴cosx=-3/5,tanx=-4/3