2 opposite angles in a quadrilateral are congruent. Is it a parallelogram?

[Newt]

If you have a quadrilateral ABCD, where angle ABC and angle ADC are opposite of each other and congruent, are the remaining two opposite angles also congruent? I know that if both pairs of opposite angles in a quadrilateral are congruent, then the quadrilateral is a parallelogram. If a quadrilateral with two congruent opposite angles IS a parallelogram, is there a name for the theorem that proves it?

 

[Deleted member 4993]

If you have a quadrilateral ABCD, where angle ABC and angle ADC are opposite of each other and congruent, are the remaining two opposite angles also congruent? No.

I know that if both pairs of opposite angles in a quadrilateral are congruent, then the quadrilateral is a parallelogram.

If a quadrilateral with two congruent opposite (one pair) angles IS a parallelogram, .......No.

is there a name for the theorem that proves it?

.

 

[Newt]

Ok, thank you for the clarification.