Excel: How to make a curvefit to sin^4(x) in office 2007 - or any freeware to do it?

I need to fit some data to a sine to the fourth and I can’t get a user defined option in excel (or maybe I’m blind?) - Any of you guys know how to do it or know of any freeware programs that can do the same?

Thanks!

If you need the model in the form of y = a (sin x)^4 + b you can simply plot y vs (sin x)^4 , but if you want a model in the form of y = a(sin wx + phi)^4 +b that is hard. Will this help: http://forums.ni.com/ni/board/message?board.id=170&message.id=236070

Excel sucks for statistics. Ideally you’d use R instead, but if you have a deadline, the learning curve might be an issue.

sin[sup]4/sup is sort of an unusual function to be regressing against. What makes you think that it’s the right model here?