三角函数求解!难题我采纳!10.化简.(1)【sin(2π-α)cos([π/2]+α)cos([π/2]-α)】/【sin(3π-α)sin(-π-α)sin([π/2]+α)】(2)【an(2π-θ)sin(2π-θ)cos(6π-θ)】/【(-cosθ)sin(5π+θ)】11.已知tanα=-2,求sin^2α-4sinαcos
来源:学生作业帮助网 编辑:作业帮 时间:2024/08/27 22:17:02
![三角函数求解!难题我采纳!10.化简.(1)【sin(2π-α)cos([π/2]+α)cos([π/2]-α)】/【sin(3π-α)sin(-π-α)sin([π/2]+α)】(2)【an(2π-θ)sin(2π-θ)cos(6π-θ)】/【(-cosθ)sin(5π+θ)】11.已知tanα=-2,求sin^2α-4sinαcos](/uploads/image/z/8759712-48-2.jpg?t=%E4%B8%89%E8%A7%92%E5%87%BD%E6%95%B0%E6%B1%82%E8%A7%A3%21%E9%9A%BE%E9%A2%98%E6%88%91%E9%87%87%E7%BA%B3%2110.%E5%8C%96%E7%AE%80.%EF%BC%881%EF%BC%89%E3%80%90sin%282%CF%80-%CE%B1%29cos%28%5B%CF%80%2F2%5D%2B%CE%B1%29cos%28%5B%CF%80%2F2%5D-%CE%B1%29%E3%80%91%2F%E3%80%90sin%283%CF%80-%CE%B1%29sin%28-%CF%80-%CE%B1%29sin%28%5B%CF%80%2F2%5D%2B%CE%B1%29%E3%80%91%EF%BC%882%EF%BC%89%E3%80%90an%282%CF%80-%CE%B8%29sin%282%CF%80-%CE%B8%29cos%286%CF%80-%CE%B8%29%E3%80%91%2F%E3%80%90%28-cos%CE%B8%29sin%285%CF%80%2B%CE%B8%29%E3%80%9111.%E5%B7%B2%E7%9F%A5tan%CE%B1%3D-2%2C%E6%B1%82sin%5E2%CE%B1-4sin%CE%B1cos)
三角函数求解!难题我采纳!10.化简.(1)【sin(2π-α)cos([π/2]+α)cos([π/2]-α)】/【sin(3π-α)sin(-π-α)sin([π/2]+α)】(2)【an(2π-θ)sin(2π-θ)cos(6π-θ)】/【(-cosθ)sin(5π+θ)】11.已知tanα=-2,求sin^2α-4sinαcos
三角函数求解!难题我采纳!
10.化简.
(1)【sin(2π-α)cos([π/2]+α)cos([π/2]-α)】/【sin(3π-α)sin(-π-α)sin([π/2]+α)】
(2)【an(2π-θ)sin(2π-θ)cos(6π-θ)】/【(-cosθ)sin(5π+θ)】
11.已知tanα=-2,求sin^2α-4sinαcosα+5cos^2α的值;
三角函数求解!难题我采纳!10.化简.(1)【sin(2π-α)cos([π/2]+α)cos([π/2]-α)】/【sin(3π-α)sin(-π-α)sin([π/2]+α)】(2)【an(2π-θ)sin(2π-θ)cos(6π-θ)】/【(-cosθ)sin(5π+θ)】11.已知tanα=-2,求sin^2α-4sinαcos
10.化简.
(1)【sin(2π-α)cos([π/2]+α)cos([π/2]-α)】/【sin(3π-α)sin(-π-α)sin([π/2]+α)】
=[-sinα(-sinα)sinα]/(sinα*sinα*cosα)=tanα
(2)【tan(2π-θ)sin(2π-θ)cos(6π-θ)】/【(-cosθ)sin(5π+θ)】
=-tanθ(-sinθ)cosθ/[cosθ(-sinθ)]
=-tanθ
11.已知tanα=-2,求sin^2α-4sinαcosα+5cos^2α的值;
∵tanα=-2 ∴sinα/cosα=-2
∴sinα=-2cosα代入 sin²α+cos²α=1
∴ 4cos²α+cos²α=1 ,cos²α=1/5,sin²α=4/5
∴ sin^2α-4sinαcosα+5cos^2α
=4/5+8cos²α+1=12/5+1=17/5
1. = -sinA*sinA*sinA/(sinA*sinA*(-cosA)) = tanA
(2) ...
sin^2 - 4sincos + 4cos^2 = (sin-2cos)^2 = cos^2 (tan-2)^2 = 16 cos^2 A
原式=17 cos^2 A
tanA = sinA/cosA = sqrt(1-cos^2)/cos
tan^2 A = (1-cos^2) / cos^2 = 2
cos^2 = 1/3
17 cos^2 A = 17/3