If so:

The result of the expression after dividing the vector by the modulus of the vector should be the unit direction vector on this vector, so all three vectors are derived from the same point B. The directions of vectors BA and BC are different, but the length is the same. So the prerequisite is that vector AB= vector DC, which tells us that it is a parallelogram (a group of opposite sides are parallel and equal), and with the inference just now, it forms a rhombus (a parallelogram with equal sides is a rhombus).

It is further deduced that the side length is 1 unit with the root sign, the diagonal line is 3 units with the root sign, and the angles of the diamond are 120 degrees and 60 degrees, and then we calculate the modulus length of AB vector as the root sign 2 (because AB = (1, 1)).

So the area is s = | ba ||| BC | sin60 = root number 3.