Sorted independent finance guides are full of helpful information on everyday money matters.

# Casio fx-991EX Classwiz: Simple Programming With Mutli-Statements

Casio fx-991EX Classwiz:  Simple Programming With Mutli-Statements

Formula Programming

With the use of the [CALC] key and multi-statment feature on the Casio fx-991EX, we can make simple temporary formula programs for repeated calculations.   Emphasis is on the word temporary:  once we go on to another mode, or press [ ON ],  the formula disappears.

There are also no comparison operators or loops to work with.

Given these limitations, we can still program simple formulas with the fx-991EX.

You are going to want to be in Norm mode for this.

Note:  This feature is present on other advanced solar calculators, however we will focus on the fx-991 EX Classwiz.

Let’s illustrate formula programming with some examples.

Formula 1

Let’s start with a simple example.

B(A) = 2A² + 1
C(B) = B/(B – 1)

To assign variables in multi-step calculations, use the syntax:

var = value.

The equals symbol can be found by pressing pressing [ALPHA] [CALC] ( = ).  This is NOT the same as the equals key on the bottom right hand corner of the keyboard.

Each calculation is separated by a colon (:).  Type a colon by pressing [ALPHA] [ ∫ ] ( : ).

Set up:

B=2A²+1:C=B÷(B-1)

Each variable that is not assigned will be prompted for in the order that they are typed.  In the expression above, B and C are assigned while A is not.   Pressing [CALC] will prompt the user to enter a value for A.

Keystrokes:

[ALPHA] ( B ) [ALPHA] ( = ) 2 [ALPHA] ( A ) [ x² ] [ + ] 1 [ALPHA] ( : ) [ALPHA] ( C )  [ALPHA]  ( = )  [ALPHA] ( B ) [ ÷ [ [ ( ] [ [ALPHA] ( B ) [  –  ] 1 [ ) ] [ CALC ]

Note:  For this to work, press [ CALC ], not the EXE key.

You will be prompted for A.  The results for B and C will be displayed.

Examples

Example 1:  A = 3
[CALC],  enter 3, press [ = ]
B:  19,  press [ = ]
C:  19/18  [ S ←→ D ] 1.0555555556

Example 2:  A = -6
Results:  B = 73,  C = 73/12 ≈ 1.013888889

R-C Circuit:  Voltage Charge and Discharge

The charge and discharge of an R-C time circuit are described by the following equations:

Charge = Y / ( 1 – B)
Discharge = Y / B

where B = e^(-A / (C*X))

Inputs:
A = time (s)
X = resistance (kΩ)
C = capacitance (μF)
Y = voltage across the capacitor (V)

In this example, B is going to be used as the temporary variable.

Set up:

B=e^(-A÷(Cx)):Y÷(1-B):Y÷B

[CALC]

Example

Inputs:
A = 5 s
C = 2.6 μF
x = 10 kΩ
y = 30 V

Results:
B = 0.825052967 (sub-formula, press [ = ] )
171.4804732 V  (voltage charge, press [ = ] )
36.36130188 V (voltage discharge)

Solar Energy:  % of Solar Light Reflected

The proportion of solar light reflected off the surface is calculated by:

T = 1/2 ( sin(E – F)^2 / sin(E + F)^2 + tan(E – F)^2 / tan(E + F)^2 )

where

E = the angle of incidence (θi)
F = the angle of refraction (θt)

We can use Snell’s law in connection with the equation above.

Since both  E-F and E+F repeat, we can assign temporary variables, such as:
A = E – F
B = E + F

Therefore:
T = 1/2 ( sin(A)^2 / sin(B)^2 + tan(A)^2 / tan(B)^2 )

And the set up for the fx-991EX Classwiz is:

A=E-F:B=E+F:1÷2*(sin(A)²÷sin(B)²+tan(A)²÷tan(B)²)   [CALC]

Example:

For this example, the calculator is Degrees mode.
Inputs:
E = 35° (θi)
F = 22° (θt)

Results:
A = E-F = 13
B = E+F = 57
0.04721102683  (% of reflected light)

Source (for R-C Circuit and Solar Energy)

Rosenstein, Morton  Computing with the Scientific Calculator  Casio.  1986. ISBN: 978-1124164130

Eddie

All original content copyright, © 2011-2019.  Edward Shore.   Unauthorized use and/or unauthorized distribution for commercial purposes without express and written permission from the author is strictly prohibited.  This blog entry may be distributed for noncommercial purposes, provided that full credit is given to the author.