Let A, B, C, D be four concyclic points in order in which AD:AB = CD:CB. If A, B, C are represented by complex numbers a, b, c, respectively, find the complex number associated with point D.
In a triangle ABC, the side lengths BC, CA and AB are consecutive positive integers in increasing order. Let $z_1$, $z_2$ and $z_3$ be the affixes of vertices A, B and C respectively in argand plane, such that $\arg\left(\frac{z_1 - z_3}{z_2 - z_3}\right) = 2\arg\left(\frac{z_3 - z_1}{z_2 - z_1}\right)$. Find the biggest side of the triangle.