已知tanθ=3,求(3cosθ-5sin^2θcosθ)/sin(π-θ)的值

来源:学生作业帮助网 编辑:作业帮 时间:2024/05/05 06:37:07
已知tanθ=3,求(3cosθ-5sin^2θcosθ)/sin(π-θ)的值

已知tanθ=3,求(3cosθ-5sin^2θcosθ)/sin(π-θ)的值
已知tanθ=3,求(3cosθ-5sin^2θcosθ)/sin(π-θ)的值

已知tanθ=3,求(3cosθ-5sin^2θcosθ)/sin(π-θ)的值
已知tanθ=3
(3cosθ-5sin^2θcosθ)/sin(π-θ) = - 1/2
楼上的:
(3cosθ-5sin^2θcosθ)/sin(π-θ)
=(3cosθ-5sin^2θcosθ)/sinθ
=(3cosθ/cosθ-5sin^2θcosθ/cosθ)/(sinθ/cosθ)
=(3-5sin^2θ)/tanθ
=(3-5sin^2θ)/3
都是对的,以下错了:
=(3-9/10)/10
=(21/10)/10
=21/100

tanθ=3
sinθ=±3√10/10
sin^2θ=9/10
(3cosθ-5sin^2θcosθ)/sin(π-θ)
=(3cosθ-5sin^2θcosθ)/sinθ
=(3cosθ/cosθ-5sin^2θcosθ/cosθ)/(sinθ/cosθ)
=(3-5sin^2θ)/tanθ
=(3-5sin^2θ)/3
=(3-9/10)/10
=(21/10)/10
=21/100

/