That is so "terse" it is difficult to tell what you are saying.
A circle with diameter "d" has radius d/2 and so area .
A square with diagonal d (so the it is inscribed in the circle) has sides of length and so area .
The ratio of "area of circle to area of square" is .
And the ratio of "area of square to area of circle" is , the reciprocal, of course.
But that doesn't appear to have anything to do with what you wrote. I can't make anything out of "4*d / sqrt(2) / d". What do the two "/" mean? If that was supposed to be , that is equal to . The "d"s cancel and that certainly is not the area of the square. And why is the squared in "(pi * d)^2". That is NOT the area of a circle of diameter d.