Which statement explains the Pythagorean theorem
A. If a triangle is a right triangle, then the sum of the squares of the legs is equal to the square of the hypotenuse.
B. If a triangle is a right triangle then the sum of the squares of the longest leg and the hypotenuse is equal to the square of the third side.
C. If all angles in a triangle are of equal measure, then the length of all sides will be equal
D. If the interior angles of a triangle add up to 180° ,then the sum of the legs of the triangle is equal to the square of the hypotenuse