Does someone know how to solve this problem ?

A point P within an equilateral triangle has a distance of 4, 5, and 6 units respectively from the vertices. Determine the lengths of the sides of the equilateral triangle.

Got far as generating 3 equations with 4 unknowns (3 angles, 1 side) using Cosine Law and I know it's not going to solve this one. (Wait)