Geometry/Properties

Triangle Properties

Triangle congruency.

Side-Side-Side (SSS) (Postulate 12) If three sides of one triangle are congruent to three sides of a second triangle, then the two triangles are congruent.

Side-Angle-Side (SAS) (Postulate 13)

If two sides and the included angle of a second triangle, then the two triangles are congruent.

'Angle-Side-Angle' (ASA)

If two angles and the included side of one triangle are congruent to two angles and the included side of a second triangle, then two triangles are congruent.

'Angle-Angle-Side' (AAS)

If two angles and a non-included side of one triangle are congruent to two angles and the corresponding non-included side of a second triangle, then the two triangles are congruent.

NO - Angle-Side-Side (ASS)

The "ASS" postulate does not work, unlike the other ones. A way that students can remember this is that "ass" is not a nice word, so we don't use it in geometry (since it does not work).