1. The problem asks to complete the sentence about the Pythagorean Theorem. 2. The Pythagorean Theorem states: In any right triangle, the square of the two legs (the two shorter sides) added together equals the square of the hypotenuse (the longest side). 3. The formula is: $$a^2 + b^2 = c^2$$ where $a$ and $b$ are the legs, and $c$ is the hypotenuse. 4. Therefore, the correct completion is: "According to the Pythagorean Theorem, in any right triangle the square of the two legs added together equals the square of the hypotenuse."