216. Find the set of points $M$ located inside a given triangle such that the distances from $M$ to the sides of the given triangle are equal to the sides of some triangle.
216. For distances $x, y, z$ to be the sides of a triangle, it is necessary that the inequalities $x<y+z, y<z+x, z<x+y$ are satisfied. However, the set of points for which, for example, $x=y+z$, is a segment with endpoints at the feet of the angle bisectors (at the feet of the angle bisectors, two distances are equal, and the third is zero, so the equality is satisfied; and from the previous problem, it follows that this equality is satisfied for all points of the segment).

Answer: the desired set consists of points located inside the triangle with vertices at the feet of the angle bisectors.