Any suggestion? (1 Viewer)

[lyounamu]

Ok, here is a deal. I always get these "prove that the quadrilateral is a parallelogram" question.

Can I just prove that they are parallelogram by saying that the opposite angles are equal? (or the opposite sides are equal?)

Is that proof all we need?

 

[RohanZ]

Yeah, I guess so.

 

[Trebla]

Ok, here is a deal. I always get these "prove that the quadrilateral is a parallelogram" question.

Can I just prove that they are parallelogram by saying that the opposite angles are equal? (or the opposite sides are equal?)

Is that proof all we need?

With the opposite sides are equal, you need to prove both pairs of opposite sides are equal, not just one. A trapezium can have one pair of opposite sides equal, so it is necessary that you prove both.
Similar case for opposite angles are equal. A kite can have one pair of opposite angles equal so you need to prove both pairs of opposite sides are equal.
Alternatively, you could prove, depending on the problem:
- both pairs of opposite sides are parallel
- one pair of opposite angles and one pair of opposite sides equal
- diagonals bisect each other

 

[henry08]

Its all I ever do.