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# [Maths] Section B Questions

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## Section B Questions

How to find A'C?
Does the shadow possesses the same angle?

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 Konus 高級學徒 發短消息 加為好友 當前離線 2# 大 中 小 發表於 2010-4-5 09:21 PM (第 3024 天) 只看該作者 AB=50m tan30'=AB/A'B A'B=86.6m Angle ABC=130' Given angle XAB=40' YBA=40' (alt angle , XA//NB) Cosine Laws AC^2=AB^2+BC^2-2(AB)(BC)cos130' ??????????? 附件: 您所在的用戶組無法下載或查看附件 UID134197 帖子133 精華0 積分14 閱讀權限20 在線時間142 小時 註冊時間2009-11-5 最後登錄2012-12-19  查看詳細資料 TOP
 nearly_crazy 高級學徒 發短消息 加為好友 當前離線 3# 大 中 小 發表於 2010-4-5 09:29 PM (第 3024 天) 只看該作者 angleA'BC=90 ,because ABC is standing vertically on the ground, so angle ABC is 90. And angle A'BC is the shadow of ABC so angleA'BC is also 90. Obviously, if you have found the length of A'B, you can use the pyth. thm. to find A'C UID91324 帖子139 精華0 積分16 閱讀權限20 在線時間109 小時 註冊時間2008-12-18 最後登錄2018-5-21  查看詳細資料 TOP
##### 引用:

angleA'BC=90 ,because ABC is standing vertically on the ground, so angle ABC is 90. And angle A'BC is the shadow of ABC so angleA'BC is also 90.

Obviously, if you have found the length of A'B, ...
I calucated just like you said when i attempt this question,but it was wrong.