To find out if three lengths are the sides of a triangle we need to remember that the triangle inequality theorem. This theorem states that: the sum of two side lengths of a triangle is always greater than the third side.
This means that:
![a+b>c](https://img.qammunity.org/2023/formulas/mathematics/college/79e6x4cb66qeh2ujjc94z0lf2m80ii4sb0.png)
For the lengths a=13 b=13 and c=1 we notice that:
![\begin{gathered} 13+13>1 \\ 26>1 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/vkb1p76wcyf3kz0vhiehan8ww9o48isbwe.png)
This means that this lengths can be the side of a triangle.
This triangle is an acute, isosceles triangle.