We can use the Pythagorean Theorem to help determine if a triangle is a right triangle, if it is acute, or if it is obtuse. ... Conversely, if \begin{align*}a^2 + b^2 < c^2\end{align*}, then lengths \begin{align*}a, \ b\end{align*}, and \begin{align*}c\end{align*} make up the sides of an obtuse triangle.
