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已知tanα=2,则sin^2α-sinαcosα的值为
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sin^2α-sinαcosα
=(sin^2α-sinαcosα)/(sin²α+cos²α) (sin²α+cos²α=1)
=(tan²α-tanα)/(tan²α+1) (上下同时除以cos²α化切)
=(4-2)/(4+1)
=2/5
=(sin^2α-sinαcosα)/(sin²α+cos²α) (sin²α+cos²α=1)
=(tan²α-tanα)/(tan²α+1) (上下同时除以cos²α化切)
=(4-2)/(4+1)
=2/5
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