vector calculus

I've done most of the question, i'm just struggling with finding the value of n. I tried putting the constant vector a in components and the vector r, but it gets really hard to do the differentiation. The question says "hence", but i don't seem to know how to apply the previous parts to find n.

I think i managed to find it, if it is n = -4?

(edited 10 years ago)

Not quite, but you're close. The "Hence" follows because the thing whose divergence you're taking is the product of a scalar function and a vector function, and so you can use the previous parts (specifically part 1) to split that divergence up into the divergence of simpler things and the grad of simpler things. You'll find that you've handily already calculated the grad of everything you need the grad of.

Reply 2

amy1e3

OP

Original post by Smaug123

Not quite, but you're close. The "Hence" follows because the thing whose divergence you're taking is the product of a scalar function and a vector function, and so you can use the previous parts (specifically part 1) to split that divergence up into the divergence of simpler things and the grad of simpler things. You'll find that you've handily already calculated the grad of everything you need the grad of.

What did you end up with for n?