Texas Instruments TINSPIRECX manual History Lesson, Approximate Calculations

First Steps with TI-Nspire™

Tutorial 2: The Calculator Application

A History Lesson

You will have noticed that, as new expressions are entered, previous ones scroll off the top of the screen. The TI-Nspire handheld will remember a history of up to 99 expressions and these can be recalled using the up key on the Touchpad. Press and hold £ and see the way the highlight flicks back through previous expressions and results. Stop at some point in the history and press ·. You should see either the previous expression or the result copied to the entry line ready to be used as all or part of a new expression.

Notice that, after an expression has been evaluated, simply pressing · again repeats the previous entry. What would you expect to see if you repeatedly pressed · on this screen? Try it by pressing

1· lv1¢+1

···…

Notice how entering an operation at the beginning of an expression (the power operation in this example) causes the automatic entry of Ans, standing for the previous answer.

If you ever need to clear the history there is an option in the Actions submenu: press b15. This is also a way of producing an uncluttered screen for making screenshots such as the one above.

Approximate Calculations

If you repeat the key sequence above but replace the first · with /· you get the rather different results shown here. Try it and continue pressing · until you get an (apparently) unchanging approximation for the Golden Ratio.

The default mode for calculations is to give exact results (using fractions) rather than approximate results (using decimals). It is possible to alter this using the system settings as you will see later in this tutorial.

Another way of choosing a decimal result is to enter a decimal

in the expression that you type, e.g. try entering 1 / 7 and then 1.0 / 7.

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