In the parallelogram ABCD, diagonals AC and BD intersect at point E.
According to the definition of parallelogram, opposite sides are equal and parallel to each other. That means, AB = DC
Now as AB and DC are parallel, so according to the property of Alternate Interior Angles, we will get:
∠EAB = ∠ECD and ∠EBA = ∠EDC
Thus , in two triangles ΔABE and ΔDCE, two angles and one side are equal. So, ΔABE and ΔDCE are congruent to each other.
That means, AE = CE and BE = DE
So, AE is congruent to CE and BE is congruent to DE
