I am having a hard timne getting my head around a problem involving double integrals, was hoping someone more learned the myself could nudge me in the right direction.
ok, suppose we have,
Now, define as
Now, in simple terms this is just
Its when I substitute for that i get problems...
I can see that the this extra factor comes from integrating twice.... but i dont understand why it comes about .
Any help would be most appreciated.