# Homework Help: Vector, cross product, and integral

1. Feb 22, 2008

### foxjwill

[SOLVED] Vector, cross product, and integral

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

$${\int \textbf{F} \times \texttt{d}\textbf{v}}.$$

$$\textbf{F}$$ and $$\textbf{v}$$ are both vector fields in $$\mathbb{R}^3$$
2. Relevant equations

$$\texttt{d}\textbf{v} = (\nabla \otimes \textbf{v} ) \texttt{d}\textbf{r}$$

3. The attempt at a solution
$$\begin{array}{ll} \textbf{F} \times \texttt{d}{\textbf{v}} &= \left( { \begin{array}{c} {F_2 \texttt{d}v_3 - F_3 \texttt{d}v_2 } \\ {F_1 \texttt{d}v_2 - F_2 \texttt{d}v_1 } \\ {F_1 \texttt{d}v_3 - F_3 \texttt{d}v_1 } \\ \end{array} \right ) \\ &= \left( \begin{array}{c} {F_2 \nabla v_3 \cdot \texttt{d}{\textbf{r}} - F_3 \nabla v_3 \cdot \texttt{d}{\textbf{r}}} \\ {F_1 \nabla v_2 \cdot \texttt{d}{\textbf{r}} - F_2 \nabla v_1 \cdot \texttt{d}{\textbf{r}}} \\ {F_1 \nabla v_3 \cdot \texttt{d}{\textbf{r}} - F_3 \nabla v_1 \cdot \texttt{d}{\textbf{r}}} \\ \end{array} \right) \\ \end{array}$$

This can then be solved as three path integrals over some path $$\textbf{r}$$. Is this correct?

2. Feb 22, 2008

### HallsofIvy

Yes, that is correct.