Pythagorean theorem says - In a right-angled triangle , the square of the hypotenuse is equal to the sum of the squares of the perpendicular and the base.
Or lets understand if hypotenuse of a right angle triangle is c and perpendicular & base is a and b respectively then as per Pythagorean theorem - a^2 + b^2 = c^2
or
Which Greek mathematician, from the 1st century BC, is best known for the theorem which bears his name and for leading a group who discovered square numbers and proposed that the earth was round, planets have an axis, and they travel around the sun?