F4 circle
2012-03-18 1:58 am
圖片參考：http://imgcld.yimg.com/8/n/HA00227359/o/701203170065713873449930.jpg
In the figure, A is a point on the major arc BC, arcAB = arcAC and ∠BAC = x.
(a) Find the possible range of x.
Ans: 0° ﹤ x ﹤ 90°
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回答 (1)
2012-03-18 2:27 am
✔ 最佳答案
Let angle AOB = y, so angle AOC = y (same arc length).Angle BOC = 2 x angle BAC = 2x ( angle at center is twice angle at circumference).
So y + y + 2x = 360 degree.
2y + 2x = 360
x + y = 180.
Max. of y = 180, so min. x = 180 - 180 = 0 degree.
For A to be always on the MAJOR arc, BC can be the diameter of circle at the limit, so min. y = 90, so max. x = 90 degree.
So 0 < x < 90.
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原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20120317000051KK00657