Ok so:

Its a 3 part question. I've completed parts 1 and 2.

Part 1)

Draw and on the same graph

Part 2)

Find between limits k and 0 (where k > 0) which gives you

Part 3) though...

I need to show between tanhk and 0 is

If you integrate it by parts you form: and I t hink between the same limits. I can't work out how to link lncoshk and that integral. And with the previous parts in the question.

Thanks in advance!

P.S How do you do an integral sign on this forum :p