# Homework Help: Scalar multiplication of two equal vectors

1. Nov 18, 2008

### transgalactic

i have vector "a"

why a*a=1??

it make no sense

the formula says |a|*|a|*cos0=a^2 (not 1)

2. Nov 18, 2008

### tiny-tim

Hi transgalactic!
But cos0 = 1,

so that means |a|*|a| = a^2, which is correct.

Where does your a*a=1 come from?

3. Nov 18, 2008

### transgalactic

from my professor in physics :(

4. Nov 18, 2008

### tiny-tim

Well, what was the context, then?

What else was he/she talking about at the time?

Unit vectors? Basis vectors? General vectors? Hilbert spaces?

5. Nov 18, 2008

### transgalactic

he just stated that if we multiply scalarly a vector(in general) by itself
we will get 1

6. Nov 18, 2008

### tiny-tim

hmm … that's obviously rubbish …

i suppose he must have been thinking of applying that to some specific equation that he didn't actaully mention.

7. Nov 18, 2008

### transgalactic

ill try to confront him with this problem

8. Nov 18, 2008

### HallsofIvy

Are you sure he didn't say a unit vector?

9. Nov 18, 2008

### transgalactic

unit vector represents a single unit with the direction of a certain axes
i think you are correct
why their multiplication equals 1?

nobody said their length is 1
only that its the smallest unit of length with a direction

??