Same Size, Same Shape
Part of the Congruence & Proof section of Coddy's Geometry journey. Lesson 6 of 63.
Two triangles are congruent when one fits exactly on top of the other: same size, same shape. You may slide it, turn it or flip it over, but not stretch it. The sign ≅ means "is congruent to".
The order of the letters is part of the statement. △ABC ≅ △DEF says A lands on D, B on E and C on F: first letter to first letter, second to second, third to third. So △ABC ≅ △DEF and △BCA ≅ △EFD say the same thing, but △ABC ≅ △EDF says something else.
Trust the letters, not the picture. The second triangle may be turned or flipped, so the matching corner is not always in the same place on the page.
Challenge
You are given △PQR ≅ △UST. Tap the point of △UST that matches Q, then press Check.
Try it yourself
Find the right part on the figure
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Congruence & Proof
1What a Proof Is
Given and ProveStatements and ReasonsChaining Equal PartsYour First Full ProofRecap: A Chain of Reasons2Congruent Triangles
Same Size, Same ShapeMatching SidesMatching AnglesWhat Congruence GivesRecap: Matching Parts8Proofs with Vertical Angles
Vertical Angles in ProofsThe BowtieBowtie with ASALinear Pairs in ProofsRecap: Vertical Angles