triangle proofs

Question

Write a two-column proof. 

Given: Triangle ACD is isosceles; <1 is congruent to <3

Prove: Segment AB || Segment CD

Answer 1

A triangle is labeled sides a, b, and c. "a" is shortest; "c" is the hypotenuse.

" angles α(alpha), β(beta), γ(gamma). α opposite side "a". β opposite "b". γ side "c".

An isosceles has 2 = sides. To make it into 2 rt triangles; draw a line from "α" down to intersect side "a" at a rt angle.

There is no parallel sides.

As for a pair of congruent triangles; the corresponding sides/angles are at the same formula. Corresponding sides are ιι.