HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 11

5 KEYS & NOTATION CONVENTIONS There are a number of types of keys/buttons that are used on the hp 39gs and hp 40gs. The basic keys are those that you see on any calculator including scientific ones, such as the numeric operators and the trig keys. Most of these keys have two or more functions, with the second function accessed via the SHIFT key and the alphabetic character accessed via the ALPHA key. Take for example the COS key shown left. If you just press the key, you get the COS function. However above left of the key and below right you will see two additional meanings assigned via the SHIFT and ALPHA keys. In this book, all references to buttons, whether they need the SHIFT key or not, are written in this typeface: KEY. The SHIFT and ALPHA keys The SHIFT key gives you the second function for each key. In the case of the COS key, the second function is ACOS, sometimes referred to as arc-cos or cos-1 or inverse cos. Most keys have these second functions that are obtained via the SHIFT key. Note: When I want you to use one of these keys that needs to have the SHIFT key pressed first I usually won't say so. It seems to me that you're intelligent enough to work out for yourself when the SHIFT key needs to be pressed. The ALPHA key The next modifier key is the ALPHA key. This is used to type alphabetic characters, and these appear below and right of most keys. Pressing SHIFT before the ALPHA key will give lower case alphabetic characters. In many views the calculator can be locked in ALPHA mode using one of the screen keys. You can also simply hold down the ALPHA key. 11