Two triangles are congruent if they have the exact same size and shape. If you can slide, flip, or rotate one triangle so it fits perfectly on top of the other, they are congruent.
Congruence Tests
You can prove two triangles are congruent without measuring all their sides and angles using these standard rules:
SSS (Side-Side-Side): All three corresponding sides are equal.
SAS (Side-Angle-Side): Two sides and the exact angle between them are equal.
ASA (Angle-Side-Angle): Two angles and the side between them are equal.
Triangle Congruence in Bridge Building
Triangles are one of the strongest shapes used in engineering. In bridges, engineers use congruent triangles because they help spread weight evenly and keep the bridge stable. Unlike squares or rectangles, triangles do not easily change shape when force is applied. Many bridges use triangle patterns called trusses.
Triangle congruence helps distribute the weight of the bridge evenly, reduce weak points, and makes the structure safer and stronger. Each triangle supports cars, trucks, people, wind forces, and vibrations. If one part experiences pressure, the force spreads through the connected triangles instead of staying in one weak spot.
Engineers use triangle congruence rulse like SSS, SAS, and ASA to prove that parts of the bridge are equal and balanced. If two support triangles have the same side lengths and angles, engineers know they will behave the same way under heavy loads.