# Homework Help: Dot product

1. Apr 14, 2010

### 8614smith

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

what is the dot product of $$G{\bullet}A$$ where A = $$\left(\frac{a_3}{l}-\frac{{a_1}}{h}\right)$$ and G = $$2{\pi}h{\frac{{a_2}}x{{a_3}}}{{a_1}{\bullet}{{a_2}}x{{a_3}}}$$

2. Relevant equations

3. The attempt at a solution

The answer is zero and ive got the worked solution infront of me, i just done see where the $$\frac{{{a_3}}}{l}$$ goes, the dot product of a vector with itself is 1 isnt it? but then where does the denominator go? and what about the denominator of G?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Apr 14, 2010

### 8614smith

sorry that first bit should say:

G = $$2{\pi}h{\frac{{a_2}x{a_3}}{{a_1}{\bullet}{a_2}x{a_3}}$$

3. Apr 14, 2010

### Staff: Mentor

No, the dot product of a vector is not 1 in general. u $\cdot$ v = |u| |v| cos([itex]\theta[\itex]).