What theorem states that, “In a right triangle, the square of the length of the hypotenuse is equal to the sum of the squares of the lengths of the legs”?

The theorem that states, "In a right triangle, the square of the length of the hypotenuse is equal to the sum of the squares of the lengths of the legs" is known as the Pythagorean Theorem. This theorem can be mathematically expressed as:

$c^2 = a^2 + b^2$

where $c$ represents the length of the hypotenuse, and $a$ and $b$ are the lengths of the other two legs of the right triangle. The Pythagorean Theorem is fundamental in geometry and has numerous applications in various fields, including architecture, physics, and engineering. It allows us to calculate the length of one side of a right triangle when the lengths of the other two sides are known.