Suppose that Quadrilateral ABCD has the property that (i) AD || BC and (ii) C and
D are on the same side of AB. Then Quadrilateral ABCD is regular.
This seems rather obvious, but I must have a proof of the above. Can someone show please. Thanks!!
In my professor lecture notes, he states:
The following says that trapezoids (defined using the American convention, as opposed to
the British convention) are regular.
Then, the proposition is stated. So I guess I still need a proof the proposition posted in my original post...