中四數學 sincostan

2010-05-16 3:12 am
sinθ+cosθ/(1+1/tanθ)
=?(ans :sinθ)

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有好多題都唔識><help me !
sin(180゚-θ) X cos(90+θ)
= ? (ans : -sin^2θ)

cos(360゚-θ) X tan(90+θ)/cosθ
= ?(-1/tanθ)
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回答 (2)

2010-05-16 4:54 am
2. sin(180゚-θ) X cos(90+θ)
=sinθ x cos [180-(90-θ)]
=sinθ x -cos(90-θ)
=sinθ x -sinθ
=sin^2θ

3.cos(360-θ) X tan(90+θ)/cosθ
=cosθ x tan(180-(90-θ)/cosθ
=cosθ x -tan(90-θ)/cosθ
=cosθ x -1/tanθcosθ
=-1/tanθ

2010-05-15 21:14:03 補充:
第1題係未(sinθ+cosθ)/(1+1/tanθ)
我計唔到

如果係~就等於
(sinθ+cosθ)/(1+1/tanθ)
=(sinθ+cosθ)/(1+1/sinθ/cosθ)
=(sinθ+cosθ)/(1+cosθ/sinθ)
=(sinθ+cosθ)/[(sinθ+cosθ)/sinθ]
=(sinθ+cosθ)xsinθ/(sinθ+cosθ)
=sinθ


收錄日期: 2021-04-16 12:55:40
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