iFxCalc: A most human nature function calculator. Support customization of functions.

Calculator 8 is a very delicate calculator that will greatly increase your calculation effectiveness. In addition to traditional calculators computing features, it offers more possibility and flexibility to calculation
This app allows you to define your own functions. So you can input expression like this:
Law_of_gravity (60, 70, 1.5)*10^7
FV(1000, 10%, 5) - 1000, etc.
You can define those complex, long or frequently used calculations as functions. Next time you can recall them conveniently. Also, you can reuse previous calculations result or whole expression very easily.
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Features:

To define a FUNTION, you only need to tell the app how it works.
For example, if we put a formula: Circle_Area=pi()*r^2
The app will automatically turn it into function: Circle_Area(r)
Turn formula "FV=PV*(1+r)^n" into function "FV(PV, r, n)", etc.
sin(30°18′)+cos(60.37°)
2. Support iOS8, iPhone6 and iPhone6Plus.
3. All users who paid this app are automatically upgraded to Pro version.