How are dot products useful?

An important use of the dot product is to test whether or not two vectors are orthogonal. Two vectors are orthogonal if the angle between them is 90 degrees ... Thus, two non-zero vectors have dot product zero if and only if they are orthogonal.

Dot product is to test whether or not two vectors are orthogonal. Two vectors are orthogonal if the angle between them is 90 degrees ... Thus, two non-zero vectors have dot product zero if and only if they are orthogonal.