we can use the Pythagorean theorem ( \(a^{2} + b^{2} = c^{2}\) ) , where a and b are the length of each of the two legs, and c is the length of the hypotenuse
\(12^{2} + b^{2} = 13^{2}\)
\(b^{2} = 169 - 144
b^{2} = 25
\sqrt{b^{2} } = \sqrt{25}
b = 5\)
the length is 5cm
