What is  || < 4 , 9 , -8 > || ?

Feb 17, 2016

The two vertical lines just mean 'the length of' the vector:

$l = \sqrt{{4}^{2} + {9}^{2} + {\left(- 8\right)}^{2}} = \sqrt{161} \approx 12.7$ units

Explanation:

Probably not a lot more explanation is needed. The formula for finding the length of a vector is something you should know because it is used very frequently.

It's probably worth noting that although this is a vector in three dimensions, it is still a square root, not a cube root.