# Show B|A| + A|B| and A|B| - B|A| are orthogonal.

1. Sep 13, 2010

### Thedream63

1. The problem statement, all variables and given/known data

Show that B|A| + A|B| and A|B| - B|A| are orthogonal.

2. Relevant equations

Orthogonal meaning at right angles

2. Sep 13, 2010

### Dick

Re: Vectors

Did you try taking the dot product of the two vectors? What should it be if they are orthogonal?

3. Sep 13, 2010

### Thedream63

Re: Vectors

Yes, but I do not know what it means by orthogonal

4. Sep 13, 2010

### Dick

Re: Vectors

It says what it means in the problem. 'Orthogonal' means the two vectors make an angle of 90 degrees, a right angle. What does that tell you about the dot product?

Last edited: Sep 13, 2010
5. Sep 13, 2010

### Thedream63

Re: Vectors

That if you add the vectors it will have a Theta of 45*?

6. Sep 13, 2010

### Dick

Re: Vectors

I think we can both agree that you have no idea what you are talking about. Could you please look up 'dot product' in your textbook or anywhere else and try and figure out what it is, and what it has to do with the angle between two vectors? Then we can talk about this further.

7. Sep 13, 2010

### TachyonRunner

Re: Vectors

When two vectors are orthogonal it means they are perpendicular to one another (90 degrees). When you take the dot product of two vectors, if they are orthogonal the dot product is zero.
For solving this question you should keep the properties of the dot product in mind.
http://www.programmedlessons.org/VectorLessons/vch07/vch07_8.html

The ones that will be most important for you are (5), (6), (7).
(1) explains why the dot product of two orthogonal vectors is zero, since cos(90) = 0.

Hope this helps.

8. Sep 13, 2010

### Thedream63

Re: Vectors

Yes i am confused and thanks to the both of you.