Question

有关高中数学必修四的某种三角函数的求值问题

要规范的答题过程哦

Answer 1

(1)∵θ∈(π/2,π)
∴tanθ<0
tanθ=-2/3
tan(θ-π/4)
=(tanθ-tanπ/4)/(1-tanθtanπ/4)
=(-2/3-1)/[1-(-2/3)*1]
=(-5/3)/(5/3)
=-1
(2) 原式=[2sinθcosθ]/[sin^2θ-3sin^2θ]
=-cosθ/sinθ
=-1/tanθ
=-1/(-2/3)
=3/2