Students discover the angle relationships formed when a transversal crosses two parallel lines — corresponding, alternate interior, alternate exterior, and same-side angles — and use them to find unknown angles.
Students will be able to…
When one line crosses two parallel lines, it creates eight angles — but only two different measures. Why, and how do you know which angles are equal?
Project this and tap each angle relationship. The diagram highlights the pair and tells you whether they are equal or supplementary.
Tap a relationship to see which angles it links.
Tap any phase to open the teacher moves and student actions.
One line crosses two parallel lines — why only two angle sizes?
Teacher models.
Class uses the Transversal Explorer.
Students find angles.
One diagram.
Aligned to the Common Core State Standards for Mathematics (High School: Geometry).
Prove theorems about lines and angles, including angles formed by a transversal.
Know precise definitions of angle and parallel lines.
Prove the slope criteria for parallel lines.
Make formal geometric constructions.
Preview the three formative checks. Tap “Sample answer” to see what mastery looks like — hide them before you print for students.
Have students set up equations when angles are given as expressions (like 2x + 10 and 3x − 20) and solve using the relationships. A printable angles sheet is in the Math library.
Tap a card to flip it, then rate whether you knew it. Built from this lesson’s vocabulary.
A quick self-check with instant feedback, drawn from this lesson’s key terms.
A print-and-go review sheet with a built-in answer key. Tap “Show answer key” to reveal answers, or print the clean version for students.