You could use pythagorean theorem to solve the problem. Look at one of the right triangle on the picture, either the right one or the left one. Pythagorean Theorem: The sum of the squares of the perpendicular sides is equal to the square of hypotenuse. a² + (2√3)² = (4√3)² a² + (2√3)(2√3) = (4√3)(4√3) a² + (4 × 3) = (16 × 3) a² + 12 = 48 a² = 48 - 12 a² = 36 a = √36 a = 6