Exercise 2 Page 175

We have been given the measures of the two angles of a triangle, $45$ and $90.$ We will find the measure of the third angle using the Triangle Angle-Sum Theorem. This theorem tells us that the measures of the interior angles of a triangle must add to $180^{\circ }.$

If we let $x$ be the unknown measure of the third angle, we can create an equation to solve for the third angle. The measure of the third angle is $45^{\circ }.$