CK-12 Foundation
Ck 12: Interactive Geometry: 4.2 Theorems About Lines and Angles
Consider two parallel lines that are intersected by a transversal, and when it crosses the two others, many different angle pairs are formed. See the special properties of the angle pairs in this interactive.
Illustrative Mathematics
Illustrative Mathematics: 8.g Find the Missing Angle
In this task, 8th graders are presented with a drawing of two parallel lines connected through two line segments. They are given the measures of two angles and are asked to find a third. Aligns with 8.G.A.5.