The properties of a parallelogram are listed below. We will use a parallelogram ABCD.
Opposite sides of a parallelogram are congruent.
The length of AB is equal to the length of DC
The length of BC is equal to the length of AD
Opposite angles of a parallelogram are congruent.
Angle A is equal to angle C
Angle B = angle D
The diagonals of a parallelogram bisect each other.
Diagonal AC ( red line ) intersects diagonal BD ( red line ) at E
Consecutive angles are supplementary or add up to 180 degrees
Angle A + angle B = 180 degrees
Angle B + angle C = 180 degrees
Angle C + angle D = 180 degrees
Angle D + angle A = 180 degrees
Each diagonal of a parallelogram turns the parallelogram into 2 congruent triangles
Triangle ABC is congruent or identical to triangle ADC
Triangle BCD is congruent or identical to triangle BAD