The equation for the Pythagorean theorem is a2 + b2 = c2 whereas the equation of a circle is (x-h)2 + (y-k)2 = r2. the two are the same speaking in terms of The entire equation is squared. If you were to solve the parentheses then essentially you're left with The Pythagorean theorem. In that sense, it's the same equation.

real world example of a circle