Students learn the shortcuts that prove two triangles are congruent — SSS, SAS, ASA, AAS, and HL — discovering how just a few matching parts can guarantee two triangles are identical.
Students will be able to…
You don’t need to check all six parts of two triangles to know they’re identical. Which combinations of just three parts are enough to guarantee it?
Project this and tap each congruence shortcut. Have students learn what parts it requires and when it applies.
Tap any phase to open the teacher moves and student actions.
How few parts do you need to know two triangles are identical?
Teacher models.
Class uses the Congruence Explorer.
Students prove congruence.
One pair.
Aligned to the Common Core State Standards for Mathematics (High School: Geometry).
Explain how the criteria for triangle congruence (ASA, SAS, SSS) follow from rigid motions.
Use the definition of congruence in terms of rigid motions.
Predict the effect of a rigid motion on a figure.
Use congruence criteria to solve problems and prove relationships.
Preview the three formative checks. Tap “Sample answer” to see what mastery looks like — hide them before you print for students.
Have students write a two-column proof showing two triangles are congruent, then use CPCTC (corresponding parts) to prove another fact. A printable proof 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.