Which is an equilateral and equiangular parallelogram ?

which is an equilateral but an not an equiangular parallelogram ?

Which is an equiangular but not an equilateral parallelogram ?

When proving that a quadrilateral is a parallelogram by using slopes you must find

Prove that equilateral traingle is equiangular.

Prove that the line segments joining the midpoints of the adjacent sides of a quadrilateral form a parallelogram.

Prove that twice the area of a parallelogram is equal in the area of another parallelogram formed by taking as its adjacent sides of the diagonals of the former parallelogram.

By using vectors prove that a quadrilateral is a parallelogram if and only if the diagonals bisect each other.