【急】已知向量a=(sinθ,cosθ-2sinθ),b=(1.2)1)若向量a平行向量b,求tanθ的值.(((答案:1/4)))(2)若|向量a|=|向量b|,0
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![【急】已知向量a=(sinθ,cosθ-2sinθ),b=(1.2)1)若向量a平行向量b,求tanθ的值.(((答案:1/4)))(2)若|向量a|=|向量b|,0](/uploads/image/z/2476583-71-3.jpg?t=%E3%80%90%E6%80%A5%E3%80%91%E5%B7%B2%E7%9F%A5%E5%90%91%E9%87%8Fa%3D%28sin%CE%B8%2Ccos%CE%B8-2sin%CE%B8%29%2Cb%3D%281.2%291%29%E8%8B%A5%E5%90%91%E9%87%8Fa%E5%B9%B3%E8%A1%8C%E5%90%91%E9%87%8Fb%2C%E6%B1%82tan%CE%B8%E7%9A%84%E5%80%BC.%28%28%28%E7%AD%94%E6%A1%88%EF%BC%9A1%2F4%EF%BC%89%EF%BC%89%EF%BC%89%282%29%E8%8B%A5%7C%E5%90%91%E9%87%8Fa%7C%3D%7C%E5%90%91%E9%87%8Fb%7C%2C0)
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【急】已知向量a=(sinθ,cosθ-2sinθ),b=(1.2)1)若向量a平行向量b,求tanθ的值.(((答案:1/4)))(2)若|向量a|=|向量b|,0
【急】已知向量a=(sinθ,cosθ-2sinθ),b=(1.2)
1)若向量a平行向量b,求tanθ的值.(((答案:1/4)))
(2)若|向量a|=|向量b|,0
【急】已知向量a=(sinθ,cosθ-2sinθ),b=(1.2)1)若向量a平行向量b,求tanθ的值.(((答案:1/4)))(2)若|向量a|=|向量b|,0
(sinθ^2+(cosθ-2sinθ)^2=5
1+4(sinθ)^2-4sinθcosθ=5
(sinθ)^2-sinθconθ-1=0
(cosθ)^2+sinθcosθ=0
cosθ(cosθ+sinθ)=0
1 cosθ=0
θ=π/2
2 cosθ+sinθ=0
tanθ=-1
θ=3π/4