Which concept is used to prove that the opposite sides of a parallelogram are congruent? congruent rectangles similar rectangles congruent triangles similar triangles

The correct answer is:

Congruent triangles.

Explanation:

Consider the top and bottom sides of the parallelogram parallel lines. The diagonal of the parallelogram would be the transversal.

The diagonal splits each opposite angle into two pieces. Using the diagonal as a transversal means we have two pairs of alternate interior angles; this means each pair is congruent. This gives us two congruent angles in two triangles.

The diagonal of the parallelogram is congruent to itself. This gives us two angles and the side between them; this is the angle-side-angle, or ASA, congruence theorem. This proves that the two triangles are congruent.

Since the two triangles are congruent, the corresponding parts of each triangle would be congruent; this means the opposite sides of the parallelogram are congruent.

I think it's congruent triangles