OBM 1989 Problem 1

The sides of a triangle $T$ , with vertices $(0,0)$ , $(3,0)$ and $(0,3)$ are mirrors.

Show that one of the images of the triagle $T_1$ with vertices $(0,0)$ , $(0,1)$ and $(2,0)$ is the triangle with vertices $(24,36)$ , $(24,37)$ and $(26,36)$ .