We can see from the given diagram that the quadrilateral ABCD is inscribed in a circle.
Now using the property:
'Opposite angles in any quadrilateral inscribed in a circle are supplements of each other'. Which means that their measures add up to a total of 180 degrees.
You know how a puppy is a kind of dog, but not all dogs are puppies? Well, the same thing is true for lots of other categories of things, including squares and rectangles.
