## Geometry: Common Core (15th Edition)

$m\angle1=117$ same-side interior
The rope represents the transversal, and the trees represent the parallel lines. The two labeled angles are same-side interior angles because they are on the same side of the rope (transvesal) and between the trees (lines). The same-side interior angle postulate tells us the two angles are supplementary. $m\angle1+63=180\longrightarrow$ definition of supplementary $m\angle1=117\longrightarrow$ subtraction property of equality