## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

The triangle is right with the hypotenuse $c=5$.
For a right triangle with legs $a$, $b$ and the hypotenuse $c$, the Pythagorean theorem states that: $$c^2=a^2+b^2.$$ We plug in the side lengths to check if the triangle is right: $$\sqrt{3^2+4^2}=\sqrt{25}=5 .$$ This statement is true, so the triangle is right with $c=5$.