Answer:
If a parallelogram has at least one 90 degree angle then its opposite angle is equal and also = 90 degrees.
The 2 remaining opposite angles add up to 180 degrees and since they must be equal, they must be 90 degrees each.
So, we have a quadrilateral with four 90 degree angles and is therefore a rectangle OR it could possibly be a square.
Step-by-step explanation:
