tan(x-π/4)=?题中没有说?
=(tanx-tanπ/4)/(1+tanxtanπ/4)
=(tanx-1)/(1+tanx)
由此可以得到tanx
则tan2x=2tanx/(1-tan^2x)
(sin2x+2cos2x)/(2cos^2x-3sin2x-1)
=(sin2x+2cos2x)/(cos2x+1-3sin2x-1)
=(sin2x+2cos2x)/(cos2x-3sin2x)
=(tan2x+2)/(1-3tan2x)
将tan2x代入即可得到值,因为题目不全,只能帮你解答到这里了