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 calculator's 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:

# Do anything a traditional calculator can do
# Reuse an earlier calculation's result or even its complete expression in your current calculation easily
# Define your own functions: 
   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.
# Insert custom functions to calculate expressions
# can enter °′″ (degrees, arc minutes and arc seconds) directly and do calculation such as:
sin(30°18′)+cos(60.37°)    
# Export custom functions to a txt file
# Use iTunes File Sharing to back up your custom functions
# Import functions from a txt file
# Share your functions to others via email
# Smart input
#  Separate versions for iPhone(3.5/4.0/4.7/5.5 inch)/iPad are available