(x-Cx)2 + (y-Cy)2 = BC2
(x-0)2 + (y-5)2 = 4.52
x2 + y2 - 10y + 19/4 = 0 .... (1)
(x-Ax)2 + (y-Ay)2 = AB2
(x-0)2 + (y-0)2 = 5.52
x2 + y2 = 121/4 ............. (2)
x2 = 121/4 - y2
上式代入 (1) 式
121/4 - y2 + y2 - 10y + 19/4 = 0
140/4 - 10y = 0
y = 14/2 = 7/2
上式代入 (2) 式
x2 + (7/2)2 = 121/4
x2 + 49/4 = 121/4
x2 = (121-49)/4
x2 = 72/4 = 18
x = 3·√2, -3·√2 (此題只要正, 故負不合).