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已知sinθ+cosθ=((√3)+1)/2,求(sinθ)/(1-(1/tanθ))+(cosθ)/(1-tanθ)的值.
人气:273 ℃ 时间:2020-01-30 17:46:56
解答
原式=[(sinθ) / (1-cotθ)] + [(cosθ) / (1-tanθ)]
={(sinθ) / [1 - (cosθ/sinθ)]} + {(cosθ) / [1 - (sinθ/cosθ)]}
={(sinθ) / [(sinθ-cosθ)/sinθ]} + {(cosθ) / [(cosθ-sinθ)/cosθ]}
=[(sinθ)^2 / (sinθ-cosθ)] + [(cosθ)^2 / (cosθ-sinθ)]
=[(sinθ)^2 / (sinθ-cosθ)] - [(cosθ)^2 / (sinθ-cosθ)]
=[(sinθ)^2 - (cosθ)^2] / (sinθ-cosθ)
=[(sinθ-cosθ)(sinθ+cosθ)] / (sinθ-cosθ)
=sinθ+cosθ
=(√3+1)/2
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