Angles in a parallelogram-Geometry Help-MooMooMath

Hi welcome to MooMooMath Today we are going to look at angles in a parallelogram
First we need to know, “ what is a parallelogram?”
A parallelogram is Quadrilateral meaning a polygon with four sides with the opposite sides parallel. We have the top parallel to the bottom (BC is parallel to AD) and (AB is parallel to DC)
This is one property that defines a parallelogram. Another property of a parallelogram is that opposite angles are congruent to each other.
Angle B will be the same measure as angle D
Let's give the angle B a measure equal to 120 degrees. Because angle D is opposite angle B it will also have an angle measure of 120 degrees. Now A and C are congruent ,but they have to have a relationship to D and B and the relationship is that these two consecutive angles are supplementary ,which means they add to 180 degrees. If angle D is 120 degrees then angle A has to be 60 degrees and angle C has to be 60 degrees. Any pair of consecutive angles of a parallelogram are supplementary.
Also, the opposite angles are congruent. Let's try a practice problem. Let's change these numbers and angle C will equal to 80 degrees. We can figure out the other three angles. What do we know about angle A ? Angle A would have to be 80 degrees and angles D and B will have to be supplementary angles to 80, so each angle would be 100 degrees. Remember, opposite angles of a parallelogram are congruent, and adjacent angles are supplementary. Hope this video was helpful on angles of a parallelogram.

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