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# OPie RPN Calc

by Andrew Swenson

### What is it about?

This is a combination RPN scientific calculator, equation plotter, one-button statistics, and linear equation solver.

### App Details

Version
1.0
Rating
(4)
Size
2Mb
Genre
Education Productivity
Last updated
March 19, 2021
Release date
March 19, 2021

### App Store Description

This is a combination RPN scientific calculator, equation plotter, one-button statistics, and linear equation solver.

RPN calculator: If not used to using an RPN calculator, search for how to use an RPN calculator on the internet. A brief description for adding and subtracting is as follows. 2+3= is performed in RPN as follows: 2 enter 3 +. Similarly, 3-1= is 3 enter 1 -. Note that in either case, you can hit the enter (or not) after the second number. The calculator has 2 main displays. The top display keeps track of all the numbers in the stack. The bottom display is where numbers are entered onto the stack and for displaying answers. For example, the following can be performed: 1 enter 2 enter 3 enter 4 enter. The stack now has 4 numbers on it from 1 to 4. Pressing + will add the last two numbers on the stack and place that result onto the stack. The stack now reads: 1, 2, 7. Pressing + again will yield 1, 9. Pressing + again will yield 10. Pressing + again will produce an error since there are not enough numbers on the stack to do the operation.

Note that the bottom display numbers can change from green to red. When the number is green, you can consider that number as part of the stack without pressing enter. However, when the number is red (usually as the result of an operation), the number is NOT part of the stack. If you want to put it onto the stack, just hit enter.

Stat Button: There has to at least be 2 numbers on the stack for the Stat Button to be enabled. From the Stat Page, you can plot the data three different ways. The Histogram allows you to change the number of bins.

E-Stk Button: Allows you to edit the numbers on the stack (delete or move). This is very useful when doing statistics with a lot of numbers on the stack and you need to correct a mistake.

Hyp/Circ Button: Switches trig functions between hyperbolic and circular

lin eq Button: Handles 2x2 to 6x6 linear equations. You do not need to fill in any zeros (blanks are treated as zeros).

Graph Mode: Can display up to 8 equations at once. The deg/rad button does affect how the trig functions are graphed (for example pi vs 180). Use the comma between equations. Press Plot, after the equations are on the display. Note, since the power buttons like x^2 and x^3 are functions inside the software, you need to be careful with parenthesis. For example: x^2 * x^3 really needs to be written as (x^2) * (x^3) in order for it to plot correctly.

C/AC Button: AC (all clear) clears everything in all modes.
Calc Mode: C clears the bottom display. If the bottom display is clear, additional C taps remove the last number in the stack.
Graph Mode: C removes the last character in the display

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