Figure: http://img814.imageshack.us/img814/68/17867979.jpg
In the figure, AB, AC and BC are three tangents touching the circle at D, E
and F respectively. If AC = 24, BC = 18 and angle ACB = 90, find the radius
of the circle.
F5 Maths
2010-10-14 8:05 pm
回答 (1)
2010-10-14 8:22 pm
✔ 最佳答案
圖片參考：http://img814.imageshack.us/img814/68/17867979.jpg
AB² = 24² + 18²
AB = 30
Let r be the radius ,
AC + BC - AB = 24 + 18 - 30
(AE + EC) + (BF + FC) - (AD + DB) = 12
(AE - AD) + (BF - BD) + EC + FC = 12
0 + 0 + EC + FC = 12
0 + 0 + r + r = 12
r = 6
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原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20101014000051KK00431