Yes the co-ordinates are right.

But the area is wrong. The area is a constant and it is 1.

I did it the long way. First let be the line joining the centers of and .

Then equation of the line is .

Now the base of the triangle is .

The perpendicular distance(height) from to the line is . So the area of the triangle is .

The perpendicular distance(height) from to the line is . So the area of the triangle is .

So the area of the quadrilateral is the sum of the area of triangles.

And that is 1, a constant.