This worksheet is about formal proof.

You can use the previously covered conditions for congruency in triangles, i.e. SSS, SAS, AAS, RHS to justify your proof.

__Example__

Prove that the triangles ADC and ABC in the following rectangle ABCD are congruent.

Use the conditions SSS, SAS, AAS, RHS to justify your proof.

**Answer**

Proof

AD = BC and DC = AB (as opposite sides of a rectangle).

AC is a common side of both triangles.

Condition SSS is satisfied.

So triangles ADC, ABC are congruent.