What is the perimeter of an equilateral triangle with an altitude of 15?

An equilateral triangle has 3 equal interior angles each of 60 degrees. There are two right angled triangles in an equilateral triangle. So we can use trigonometry to find the length of one side of the equilateral triangle then multiply this by 3 to find its perimeter. Hypotenuse (which is one side of the equilateral) = 15/sin 60 degrees = 17.32050808 17.32050808 x 3 = 51.96152423 Perimeter = 51.96152423 units.