F5 circles

2011-05-19 6:27 am

Figure: http://imageshack.us/photo/my-images/545/circled.jpg/
The figure shows the circle C:
x^2+y^2-6x-2y+9=0. l is a tangent to C. tan B =

A. 0
B. 1/2
C. 3/4
D. 4/3
E. 3/2

圖片參考：http://imgcld.yimg.com/8/n/HA00149615/o/701105180115613873440560.jpg
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回答 (1)

2011-05-19 6:32 am

✔ 最佳答案

x^2 + y^2 - 6x - 2y + 9 = 0(x - 3)^2 + (y - 1)^2 = 1=> tan(B/2) = 1/3tanB = 2tan(B/2)/[1 - (tan(B/2))^2] = (2/3)/(1 - 1/9)= 3/4 (C)

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