maths _10

👨🏻‍🏫 學術台數學

用戶114652

2009-05-17 6:31 am

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更新1:

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回答 (1)

STEVIE-G™

2009-05-17 7:50 am

✔ 最佳答案

我眼睛不太好...可唔可以放大D呢??^_^

2009-05-16 23:50:16 補充：
24)
OA=15*2=30km
AB=10*3=30km
∠OAB=180-60=120
By Cosine Law,
OB^2=OA^2+AB^2-2(OA)(AB)cos ∠OAB
OB^2=(30)^2+(30)^2-2(30)^2cos120
OB^2=2700
OB=30√3 km

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