My desk of Integrals has the final case ##int frac dx x^2+a^2 ## as being a 'common' integral far too, not merely the situation where ##a=one##. But I think this becoming a Calculus homework issue it is expected from the OP to figure out how to get it done. Hints https://gabletoppak.com/the-growing-threat-of-marine-pollution-and-how-gabletop-cartons-offer-a-solution/