(1)已知cosθ=﹣3/5,θ∈(π/2,π),求(θ+π/3)(2)已知tanα=2,求tan(α-π/4)
问题描述:
(1)已知cosθ=﹣3/5,θ∈(π/2,π),求(θ+π/3)(2)已知tanα=2,求tan(α-π/4)
答
cos(απ/4)=3/5 因为sin^x cos^x=1 00 sin(απ/4)=4/5 sinα=sin(απ/4-π/4)=sin(απ/4)cos(π/4)-cos(απ/4)csin(π/4)=(4/5)*(根号2/2)-(3/5)*(根号2/2)=根号2/10 cosα=7*根号2/10 tan α=sinα/cosα=1/7 很高兴为你解答