Pythagoras Theorem states that in a right-angled triangle, the square of the length of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the lengths of the other two sides.Mathematically, if the triangle has sides a and b, and hypotenuse c, then:c^2 = a^2 + b^2It is used to calculate distances, heights, and in many geometric and real-life applications.