Angle Bisectors (euclidean)
Here we are with our good old friend, triangle ABC. The lines in that ugly shade of purple shows the angle bisectors of the angles at each vertice. D is the intersection of these lines, and the center of our focus as well. Grab A and try to position it in a way such that D lies outside of the triangle. Having a hard time? Try the same things with B. Still no luck? I hope that by now you can guess what will happen if we try to move C. Regardless of the position of these points or form of the triangle, the intersection of the angle bisectors will always be contained by the boundaries of ABC. Check out the proof below.