Question

ABCD is a quadrilateral with AB equal and parallel to DC. prove that AD is equal and parallel to BC​

Answer 1

Answer: see below proof

Explanation:

Imagine a diagonal line AC

If AB = DC and AB // DC then angle BAC =

Angle ACD Alternate Interior angles theorem.

Then if AB = AD and angle BAC = angle ACD and AC = AC then triangle ABC is congruent to triangle CDA.

If triangle ABC is congruent to triangle CDA then AD = BC because congruent parts of congruent triangles are congruent.

If triangle ABC is congruent to triangle CDA then angle ACB = angle CAD because congruent parts of congruent triangles are congruent.

If angle ACB = angle CAD then AD // BC because of the alternate interior angles theorem.