use the pythagorean theorem to see if the measurements create a right trinangle.
remember the addition of the squared shorter sides must be equal to the largest side squared
[tex]a^2+b^2=c^2[/tex][tex]5^2+12^2=13^2[/tex][tex]\begin{gathered} 5^2+12^2=169 \\ 13^2=169 \\ \\ 169=169 \end{gathered}[/tex]