已知cotθ=1/2,求sin²θ-2sinθcosθ+3cos²θ=?
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![已知cotθ=1/2,求sin²θ-2sinθcosθ+3cos²θ=?](/uploads/image/z/8432785-1-5.jpg?t=%E5%B7%B2%E7%9F%A5cot%CE%B8%3D1%2F2%2C%E6%B1%82sin%26sup2%3B%CE%B8-2sin%CE%B8cos%CE%B8%2B3cos%26sup2%3B%CE%B8%EF%BC%9D%3F)
已知cotθ=1/2,求sin²θ-2sinθcosθ+3cos²θ=?
已知cotθ=1/2,求sin²θ-2sinθcosθ+3cos²θ=?
已知cotθ=1/2,求sin²θ-2sinθcosθ+3cos²θ=?
sin²θ-2sinθcosθ+3cos²θ
=(sin²θ-2sinθcosθ+3cos²θ)/(sin²θ+cos²θ),【分子分母同除以sin²θ】
=(1-2cotθ+3cot²θ)/(1+cot²θ)
=(1-1+3*1/4)/(1+1/4)
=3/5