In order to dertermine the intersection point O, we have that knowing the coordinates of the shape, being this ABCD (A shape with 4 sides), we can fin the intersection using:
Now, that being the coordinates of the diagonals. [This is a particular case for squares, rectangles, rhombus or prallelograms]
For nonuniform quadrilaterals, we will have:
Since the shape is not given, we will consider a quadrilateral with it's four cornes given (It's coordinates that is).
Since we know the coordinates of the shape ABCD, we can find the equation of AC & BD using:
If we solve the equations we can find the interception point O.