Steiner’s theorem

Let $ABC$ be a triangle and $M,N\in (BC)$ be two points such that$m(\mathrm{\angle }BAM)=m(\mathrm{\angle }NAC)$. Then the cevians $AM$ and $AN$ arecalled isogonic cevians and the following relation holds:

$$\frac{BM}{MC}\cdot \frac{BN}{NC}=\frac{A{B}^2}{A{C}^2}$$