Orthogonal Vectors

There are two ways to calculate a dot product.

The formula below has cosine Theta in it. We get zero if theta is 90 degrees.

$a \cdot b = |a| \: |b| cos (\theta)$

Two nonzero vectors are orthogonal to each other if their scalar product is zero.

Appendix A

Notice that it doesn’t make sense to refer to a single vector as being orthogonal. A vector has to be orthogonal to another vector.