If a parallelogram has a right angle is it a rectangle?
No because it could be an irregular quadrilateral that includes a right angle. A rectangle has four right angles.Yes, a parallelogram with a right angle is always a rectangle. In fact, in my geometry book, some 55 years ago, such was the definition of rectangle.A parallelogram with one right angle will always have four right angles.It is true that you can draw an irregular quadrilateral with a right angle which is not a rectangle but the figure will not be a parallelogram.