Hello! Has it been a fortnight already? Well I certainly know my BMI hasn't improved (for all our new folks, please refer to Homework 2). So it's time to grab your coffee and let's get into our next lesson on how to use your 9850 calculator. Once again, the important keys for this lesson can be found on the right hand side.

Lesson 3
I remember when I first started using this calculator. We had a class kit at school that was collecting dust and so I was sent by my Head Teacher to an inservice, like TiGM and run by Anthony Harradine. One of my questions for him was, 'where on earth is the memory button?' I wanted to store a number in memory that I could call back when I wanted it and there was nothing on the keypad that suggested a memory.

So Anthony said to me, 'Son, this calculator has 26 memories, one memory for each letter of the alphabet' ... Being the wise man he is, I thought this was some sort of cryptic life lesson. He went on to explain, that the red letters above the keys are variables that you can assign values.

Part 1 - Assigning a numeric value to a variable
A common HSC question in General is substituting values into an algebraic expression and calculating the answer. Take the following example:

Let's say we have the expression and you want to evaluate it when a=4 and b=-3. Take a second to think what mistakes you can see the kids making?

Grab your calculator and turn it on. Enter RUN mode by using the arrows on your keypad and press the blue EXE button (figure 1). Now the syntax for storing numbers in your calculator is:

The arrow button is located right above the AC/ON button. So let's now enter those values into A and B on our calculator. Type 4, then the arrow key, followed by the A (to get the A, you need to press the red ALPHA button, then the button with the A above it), the press EXE (figure 2). Now do it again for B by typing -3, the arrow key, ALPHA B and EXE (figure 3).

It doesn't look like much has happened but in fact the calculator has given letters A and B the value of 4 and -3 respectively.

Part 2 - Using a variable with a stored value
So let's now find the value of when a=4 and b=-3. All we need to do is type in the expression into the calculator and press EXE! (the 'squared' button is right of the ALPHA key) The answer works out to be 49 just as it should (figure 4).

Just to go a little further, try a+b and see what you get. Notice you don't have to worry about signs ... is this a good thing?

Part 3 - Some more information about the variables
Here are some dot points to help you further with using the variables on the calculator:

• When the calculator is reset, all the variables are not empty, but are set to 0.
• The value of each variable is kept when the calculator is turned off.
• There is a way of assiging values to multiple variables. Let's say we want all the memories to have a value of 0. We would type 0->A~Z and press EXE. The 'swiggle' is found by pressing ALPHA (figure 5).
• The use of variables are great for 'on-the-run' calcuations. Let's say you need to use Pythagoras to find a side, then use that number in another calculation. Instead of clearing the answer and entering it again later, why not put it in as a variable? To do this, when you press EXE to find the length of the side, follow it by pressing the arrow key, then the variable you wish to use (figure 6). Write back to me if you would like to see an example of that.

That it! Well done. Please feel free to forward any questions or comments to by replying to this email.

Marty Schmude