# HELP easy algebra vector question please!

1. Mar 26, 2009

### vorcil

1. Find a.b given the following information
|a|=3

two vectors a.b are perpendicular to eachother

b
|
|
|
|__________a

3. |a| = 3
a = squareroot of 3,

if B is a vector perpendicular to a,
dunno what to do from here,

Last edited: Mar 26, 2009
2. Mar 26, 2009

### Dr.D

You want the dot product of two vectors that are perpendicular to each other?

What is the cosine of a right angle?

Does that give you any ideas?

3. Mar 26, 2009

### Nabeshin

This doesn't make any sense. First you say the magnitude of the vector is 3, then you say it equals the square root of three?

Also, I see no question. (Might be the dot product as Dr.D suggests but I don't see it)

4. Mar 27, 2009

### Staff: Mentor

Please don't post the same problem in two different forums. You also posted this in the Calculus and Beyond forum.

5. Mar 27, 2009

### HallsofIvy

Staff Emeritus
One important application of "dot product" is determining if two vectors are perpendicular. Do you remember how?