Move the points in the grafic or define the point coordinates in the numeric field.
The opposite sides are equal. The opposite sides are parallel. The diagonals halve each other. Opposite angles are equal. Two neighbour angles have in sum 180°.
With the side length a = AB = CD and b = BC = DA the circumference is given by:
With the side length a and b and the angle α the area is given by:
With the side length a and b is the length of the diagonals given by: