# Constant vector?

1. Feb 10, 2008

### kthouz

Can someone explain me how check if a vector is a constant vector?

2. Feb 10, 2008

### disregardthat

You have to define your terms. What is a constant vector, i.e. how is it defined?

3. Feb 10, 2008

### HallsofIvy

You check if it is a vector, you check if it is constant. What more do you want? Perhaps if you gave an example of the typ of problem you are trying to do it would help.

4. Feb 11, 2008

### kthouz

've been two perpendicular vectors r and v. r=coswi + sinwj where w is a constant and i and j are unit vectors.
The problem is to show first that v is perpendicular to r and then show that r x v is a constant vector. (here x is the cross product)

5. Feb 11, 2008

### HallsofIvy

Okay, so you are given r= cos(w)i+ sin(w)j. You are also "given" v? What is v? Showing that v is perpendicular to r (for whatever v you are given) should be easy. Just take the dot product. As for a constant vector, so far you haven't mentioned any variable! Are you sure it wasn't r= cos(wt)i+ sin(wt)j where t is the independent variable?

It's really very difficult to help you if you don't tell use precisely what the problem is!