Explain the Pythagorean theorem.

A.
The Pythagorean theorem states that if a triangle is a right triangle, then the sum of the squares of its legs equals the square of its hypotenuse.
B.
The Pythagorean theorem states that if the square of one side of a triangle is greater than the sum of the squares of the other two sides, then the triangle is a right triangle.
C.
The Pythagorean theorem states that if the square of one side of a triangle is less than the sum of the squares of the other two sides, then the triangle is a right triangle.
D.
The Pythagorean theorem states that if a triangle is a right triangle, then the sum of the squares of its legs is greater than the square of its hypotenuse.

A.

The Pythagorean theorem states that if a triangle is a right triangle, then the sum of the squares of its legs equals the square of its hypotenuse.