# Thread: How to find this limit

1. ## How to find this limit

Hi, the title pretty much says it.
(I tried a few things but noting worked, I really have no idea how to do this)

Prove that

$\lim_{R \rightarrow \infty} \int \frac{dt}{cosh(R+it)}=0$ where R and t are real numbers.

Thanks so much in advance.

2. ## Re: How to find this limit

Did you put this in exponential form? Remember that the hyperbolic functions are related to the trig functions (I assume you know how, ask if you don't or look it up) and they obey identities that are reminiscent of the trig identities.