I have used chain rule so my first step is
\nabla(\vec{a}\cdot\vec{r})(\vec{b}\cdot\vec{r})=(\vec{b}\cdot\vec{r})\nabla(\vec{a}\cdot\vec{r})+(\vec{a}\cdot\vec{r})\nabla(\vec{b}\cdot\vec{r})
I think this is correct, so if ur result is true it means that \nabla(\vec{a}\cdot\vec{r}=\vec{a} ?
but i got [\vec{a}(\vec{b}\cdot\vec{r})+\vec{b}(\vec{a}\cdot\vec{r})]\nabla\vec{r}
btw i havnt done tensors yet, so I've used the basic property of \nabla
Homework Statement
Q1. Evaluate grad(f) for the function f(\underline{r})=(\underline{a} dot \underline{r}) (\underline{b} dot \underline{r})
Q2. If \underline{c} is a constant vector, show that grad |\underline{c} cross \underline{r}| ^n = n |\underline{c} cross \underline{r}| ^(n-2)...