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

1 Answer
Feb 17, 2016

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

#l=sqrt(4^2+9^2+(-8)^2)=sqrt161~~12.7# units


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.