# Cross product and the angles of a prallelogram

1. Nov 6, 2009

Cross product and the angles of a prallelogram's diameters

1. The problem statement, all variables and given/known data

With the help of cross product prove: if the angle between the diameters of a parallelogram is 90 degrees, then the parallelogram is a rectangular.

2. Relevant equations

A$$\times$$B=(surface of the parallelogram)

3. The attempt at a solution

Last edited: Nov 6, 2009
2. Nov 6, 2009

### clamtrox

What is $$|\mathbf{A} \times \mathbf{B}|$$? How does it depend on the angle between the two vectors?

3. Nov 6, 2009

A and B are not the diameters, they are the sides. As I mensioned $$|\mathbf{A} \times \mathbf{B}|$$= (the surface of the parallelogram)