## Sunday, April 3, 2016

### Casio Classpad fx-CP400: Defining Functions

Casio Classpad fx-CP400:  Defining Functions

Using the Define command with the Classpad

A lot of formulas can be created using the Define command on the Casio Classpad.  For this blog I am using the fx-CP400.  My preference is to use the Main application, and call the Define command from the Action>Command submenu.  The expressions are stored as Functions.  If you want to transfer functions (and programs) from the fx-CP400 to a computer drive, export them to the Save-F folder first and then connect the Classpad to the computer.

Fibonacci Numbers

fibon(n) = approx((1+√5)^n – (1-√5)^n)/(2^n * √5)

The approx command is used in order to force a simplified numerical answer.

Error Function

erf(z) = 2/√π * ∫ (e^-x^2 dx from 0 to z)

I think numerical integrals return approximate answers no matter what, please correct me if I am wrong.

Digital Root:  Counting all digits of a number, repeating the process until you get a single digit (0-9)

dr(n) = 1 + mod(n-1, 9)

I could only find the mod function in the catalog.  Unlike most Casio calculators, the Classpad’s mod function accepts negative numbers and non-integers.

Area of a Regular Polygon

aregpoly(n,s) = (n*s^2) / (4 * tan(180°/n))

The degree symbol (°) is needed to allow proper calculation regardless of angular mode.  The degree symbol is found in the Trig soft menu.

Great Circle: Distance between two places in kilometers

Note:

*  In order for the function to work properly, the Degree mode must be selected.

*  You can enter degrees in terms of degrees, minutes, seconds by choosing the DMS template.  This template is in the Math1 soft keyboard and is represented by three boxes (□ □ □) next to toDMS.  You can also call the template by pressing Action/Interactive, Transformation, DMS, dms.   The dms command’s syntax is  dms(degrees, minutes, seconds) and transforms the input into degree decimals.

Example:
Los Angeles,  N: 34°13’, E: -118°15’;   Tokyo,  N: 35°41’22.22”, E: 139°42’30.12”
Distance ≈ 8,803.002688 km

Formula (for km):
Distance ≈ cosˉ¹ (sin N1 sin N2 + cos N1 cos N2 cos (E1 – E2)) * 6371 * π / 180

If you want US miles, replace 6371 with 3959.

This blog is property of Edward Shore, 2016.

### HP Prime and HP 41C/DM 41L: Sum of Two Squares

HP Prime and HP 41C/DM 41L:  Sum of Two Squares  Introduction Given a positive integer n, can we find two non-negative integers x and y...