来个看似简单的数学问题，闲的来试试

ptrees

[(x - x1) * (x - x1) + (y - y1) * (y - y1)] = (r1 * r1) /k
  [(x - x2) * (x - x2) + (y - y2) * (y - y2)] = (r2 * r2) /k
[(x - x3) * (x - x3) + (y - y3) * (y - y3)]  = (r3 * r3) /k

化简一下就是2元一次方程,然后...主要懒得算了