# How do you compute the dot product to find the magnitude of #u=-21i#?

##### 1 Answer

Jan 7, 2017

#### Explanation:

It should be absolutely obvious that

We can show this using the dot product using the fact that:

#|| vec u || = sqrt (vecu * vec u) #

To get

#|| vec u || = sqrt ((-21)(-21)) =sqrt(21^2)=21#