高1数学问题
1.已知cosθ=-12/13,θ=(π,3π/2),求sin(θ-π/4),cos(θ-π/4)及tan(θ-π/4)的值?
各位谢谢了 小弟我只有那吗点分了~`````要详细的过程````如果详细可以在给你分````谢谢了
参考答案:θ=(π,3π/2),cosθ=-12/13,所以sinθ = -5/13
sin(θ-π/4)
= sinθcos(π/4)-cosθsin(π/4)
= [(√2)/2](sinθ-cosθ)
= [(√2)/2][7/13]
=7(√2)/26
cos(θ-π/4)
= cosθcos(π/4)+sinθsin(π/4)
= [(√2)/2](sinθ+cosθ)
= -[(√2)/2][17/13]
=-17(√2)/26
tan(θ-π/4)
=[sin(θ-π/4)]/cos[(θ-π/4)]
= -7/17