My homework assignment is to analyze an accounting case and write a paper about it. One of the things we need to do is define functional currency under IFRS and US GAAP, tell the main difference between the two, and give an example of a situation in which functional currency would differ between the two.
After we understand that we analyze the functional currency of the case. I researched and to me the two seem the same. I can not figure out what the difference is, both are the currency of the main economic environment of the entity. Can anyone explain the difference to me?

There are many articles available on this subject here is one of them

http://www.ato.gov.au/businesses/content.aspx?doc=/content/40861.htm