KC2 app for iPhone and iPad

A neat expression based Calculator includes awesome features on iPhone.

Feature 1:
Portrait Simple Calculator for daily addition, division, subtraction, and Multiplication.

Feature 2:
Landscape Scientific Calculator with trigonometrical, arithmetical and exponential functions.

Feature 3:
Self-define function used as built-in function, where users can define their own functions with variables (a, b, c, d) and use them as built-in function by supplying arguments for each variables according to corresponding position, like 2√(a^2+b^2) with name of Pythagorean.

Feature 4:
Formula graphing, where calculator can automatically draw a formula graphic on x-y like coordinate plate according to user formula, an expression with variable a, like sin(a).

Feature 5:
Expression recording. where calculator automatically records what users have inputed into calculator for evaluation.