Geometry: Common Core (15th Edition)

$\overline{BC}$
Let's take a look first at the angles in this triangle. We have an exterior angle, which will be supplementary to the interior angle $\angle A$; therefore, $\angle A$ of the triangle can be calculated by the following equation: $m \angle A = 180 - 85$ Subtract to find the measure of $\angle A$: $m \angle A = 95$ We know that $\angle A$ is the largest angle because the sum of the measures of the other two angles has to be $180^{\circ} - 95^{\circ}$ or $85^{\circ}$. $\overline{BC}$ would be the longest because it is opposite the largest angle in a triangle where two of the angles are not congruent.