There are two triangles, ABC and DEF. We are given that side AB is congruent to side DE, side BC is congruent to side EF, and side AC is
congruent to side DF.
There are two triangles, ABC and DEF. We are given that side AB is congruent to side DE, side BC is congruent to side EF, and side AC is
congruent to side DF.
When these conditions are met, the two triangles must be congruent, which means their corresponding angles are congruent. That is, angle A is congruent to angle D, angle B to angle E, and angle C to angle F.
This fact can be proved from the SAS postulate, using a preliminary result, known as Euclid's 7th proposition.
In this lesson you will be shown the proof of that proposition and the subsequent proof of SSS.