Sign up ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

If I have perpendicular vectors $ \vec{a}$ and $\vec{b} $, then $\vec{a}.\vec{b} = 0$. What happens if they are co-linear? Would you just get $\vec{a}.\vec{b} = ||\vec{a}||.||\vec{b}|| . 1 $?

Also, does $\vec{a}$ x $\vec{b} = 0$ if they're co-linear?

share|cite|improve this question

1 Answer 1

up vote 1 down vote accepted

For colinear vectors you have $\vec a\cdot \vec b=\pm ||\vec a||\cdot|\vec b||$. And, yes, you also have $\vec a\times \vec b=\vec 0$ for colinear 3D vectors.

share|cite|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.