# Math Help - Length of a vector

1. ## Length of a vector

Hi Math help Forum

I'm not sure if this is the right thread to be posting this in, so sorry.

the question is to calculate |a x b| where

a= i+j-k
b=2i-j+3k

I've worked out a x b to be 2i - 5j - 3k , but I'm not really sure as to where to go from here.

any help would be great

Thanks

ES

2. Originally Posted by El Sparko
Hi Math help Forum

I'm not sure if this is the right thread to be posting this in, so sorry.

the question is to calculate |a x b| where

a= i+j-k
b=2i-j+3k

I've worked out a x b to be 2i - 5j - 3k , but I'm not really sure as to where to go from here.

any help would be great

Thanks

ES
Calculate now the length (or the absolute value) of (2, -5, -3).

You should get the result $|\vec v| = \sqrt{38}$