Probability
2014-04-02 1:33 am
For a regular octagon ( 8 sides), a triangle can be drawn by joining any 3 vertices. Find the probability that the triangle so drawn is a right - angled triangle.
回答 (2)
2014-04-02 9:25 pm
✔ 最佳答案
There are 4 diameters in a regular octagon. Let AB be the diameter,where A,B are 2 vertices, then △ABP is a right - angled triangle, where P is any vertices other A and B.
As there are 6 choices of P, so 4 × 6 = 24 right - angled triangle can be formed.
The required probability = 24 / 8C3 = 24/56 = 3/7 .
2014-04-03 12:06 am
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非常好的解答，可以利用 4 條 diagonals 正正是 circumscribed circle 的 diameter，再配合 ∠ in semi-circle = 90° 就可以作出有系統的思考。
╭∧---∧╮
│ .✪‿✪ │
╰/) ⋈ (\╯
非常好的解答，可以利用 4 條 diagonals 正正是 circumscribed circle 的 diameter，再配合 ∠ in semi-circle = 90° 就可以作出有系統的思考。
╭∧---∧╮
│ .✪‿✪ │
╰/) ⋈ (\╯
收錄日期: 2021-04-24 23:23:46
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20140401000051KK00093