Question

prove that a diagonal of a parallelogram divide it into two congruent triangle

Answer 1

first, draw a parallelogram ABCD
join A and C (diagonal)

sol:
in triADC and triACB,
•angleD=angleB (opp. sides of parallelogram are eq.)
•AC=AC (common)
•angleDCA= angleCAB (alternate interior angles)
so, ASA rule, triADC is congruent to triCAB

Answer 2

I'd attached the proof in the pic.. See the pic..