If all the sides of the triangle have the same length, the triangle is equilateral. The perpendicular from one vertex (corner) to the opposite side creates two right triangles, the leg and hypotenuse of which are 25 feet and 50 feet respectively, because the perpendicular bisects the opposite side.
By Pythagoras, the length of the perpendicular is √(502-252)=√(252(4-1))=25√3=43.3 feet approx.