In a right triangle, if the lengths of the two legs (sides adjacent to the right angle) are and , and the length of the hypotenuse is , then:

Consider a right triangle where the lengths of the legs are and , and the hypotenuse is . By scaling this triangle by factors of , , and , we can create three similar triangles as shown below:

Arranging the three scaled triangles as shown forms a rectangle:

From this arrangement, it becomes evident that:

Thus, in a right triangle, the square of the hypotenuse is equal to the sum of the squares of the two legs. This property is known as the Pythagorean Theorem.