amaths 問題

Please refer to the following solution:

圖片參考：http://hk.geocities.com/stevieg_1023/S1.gif


圖片參考：http://hk.geocities.com/stevieg_1023/S2.gif


圖片參考：http://hk.geocities.com/stevieg_1023/S3.gif

vertex = (1,2)
T : 12x + 9y - 26 = 0
centre = (1,k)
circle passes through vertex, radius = k - 2
radius = ! 12(1) + 9k - 26 ! / sqrt(144 + 81) = k - 2
(9k - 14) / 15 = k - 2
9k - 14 = 15k - 30
k = 8/3
radius = 8/3 - 2 = 2/3
circle : (x - 1)^2 + (y - 8/3)^2 = (2/3)^2
(x - 1)^2 + (y - 8/3)^2 = 4/9