點解要乘sin(90-Θ)?
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maths problems
2012-10-20 9:51 pm
回答 (1)
2012-10-21 9:33 pm
✔ 最佳答案
BC = 5/tan30 = 5√3As the shadow is a parallelogram rather than retangleIts height is BC sin(90 - θ) where θ is ∠BCS We have20 * BC sin (90 - θ) = 15020 * 5√3 cos θ = 150cos θ = 150/(100√3)cos θ = √3/2θ = 30So, ∠BCE = 60 and the bearing of B from C is 90 + 60 = 150 (B)
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https://hk.answers.yahoo.com/question/index?qid=20121020000051KK00250