Formulus Free 4+

Excellent app!

This app an incredibly convenient one to own, especially if you're like me and are constantly going to google or wolfram alpha to find the mathematical formula for something you should have memorized. I highly recommend it.

I tutor calculus students for a living and this app is perfect for me - I know the material, I just can't remember all the formulas.

There is no interactivity. It's just a big PDF with a bunch of formulas and an occasional line of explanation. Beginners may frustrated in part because the organization is not great, but since it's free, you might as well have it.

The good news: there is a ton of stuff here, and it is all accurate as far as I can tell (exception: I can confirm an error in Simpson's rule that another reviewer pointed out). There is a sizable section on differential equations (including Laplace transforms), but not much on multivariable calculus.

Problem: there is a glitch with the headers. For example, when I was looking at derivatives, the header said "Algebra & Geometry."

The main complaint I have is that certain things have been overlooked. The derivative of an inverse function is missing. The section on complex numbers does not include Euler's formula. There's no mention of radius of convergence.

The list of power series expansions is too short - surely it should have cos(x), ln(x+1) and the binomial series. In the integration by parts section, why not include the tabular method? By and large, the list of integrals was shorter than I expected, but it does cover the basics.

It would be nice if this had a feature that allowed users to add their own notes (and corrections!).

But it's free, so you can't complain.