Question

What is $a$ cross $b$ cross $c$ ?

Answer 1

Cross product of three vectors:

In vector algebra, $a$ cross $b$ cross $c$ is the vector triple product and is defined as the cross product of three vectors.

Formulas for the triple product:

• $\left(a\times b\right)\times c=-c\times \left(a\times b\right)=c\times \left(b\times a\right)$
• $\left(a\times b\right)\times c=\left(c·a\right)b-\left(c·b\right)a$
• $a\times \left(b\times c\right)=\left(a·c\right)b-\left(a·b\right)c$
• If all vectors are collinear, then $a\times b\times c=0$