Question

Craig wants to prove that if quadrilateral ABCD has diagnols that biscet each other then it is a parallelogram

Answer 1

△ABE and△CDE by side-angle-side

Answer 2

Consider quadrilateral ABCD is a parallelogram. The parallelogram have diagonals AC and DB.

So in the given quadrilateral ABCD, let the diagonal AC and diagonal DB intersects at a point E.

Thus in the quadrilateral ABCD we see that :

1. AC and DB are the diagonals of quadrilateral ABCD.

2. Angle DCE is congruent to angle BAE and angle CDE is congruent to angle ABE. (they are alternate interior angles)

3. Line DC is congruent to line AB. (opposites sides are congruent in a parallelogram )

4. Angle ABE is congruent to angle CDE. (Angle side angle)

5. Line AE is congruent to line EC. And line DE is congruent to line EB. (CPCTC)

Thus we see that if the diagonals of a
`\text{quadrilateral bisects each other}`, then the quadrilateral is a parallelogram.