- #1
dingo_d
- 211
- 0
Homework Statement
Every time I pick up Jackson I feel dumb :(
So in 5.5 chapter about Circular Current Loop, he says:
[tex]|\vec{r}-\vec{r}'|=[r^2+r'^2-2rr'(\cos\theta\cos\theta'+\sin\theta\sin\theta'\cos\phi')]^{1/2}[/tex]
So it's cosine rule, but how did he got to that sine/cosine thing? It should be the angle between r and r'. I tried drawing but to no avail :\
help...