teorema de Pitágoras:
[tex]\large\boxed{\begin{array}{l} \rm \: a {}^{2} = b {}^{2} + c {}^{2} \rightarrow \begin{cases} \rm \: a = 13 \\ \rm \: b = 12 \\ \rm \: c = x\end{cases} \\ \\ \rm \: 13 {}^{2} = 12 {}^{2} + x {}^{2} \\ \\ \rm \: 169 = 144 + x {}^{2} \\ \\ \rm \: 169 - 144 = x {}^{2} \\ \\ \rm \: x {}^{2} \: = \: 25 \\ \\ \rm \: x = \sqrt{25} \\ \\ \boxed{\rm {x = 5}}\end{array}}[/tex]
