Question

Are the angles congruent If yes, how do you know?

Answer 1

From the given diagram, notice that DE is congruent to AB, EC is congruent to BC and the angles ABC and DEC are congruent.

Since two sides of the triangles and the included angle are congruent, we know from the SAS congruence theorem that ABC and DEC are congruent.

Therefore, the answer is: yes, the triangles ABC and DEF are congruent due to the SAS theorem.