Now, without doing anything else, change back to the HOME view and type X and press ENTER. The value which appears is the stored x coordinate of the last intersection point found. To find the y coordinate, evaluate F1(X) (or F2(X) - for that point the values are the same). This value can be used in calculations in the HOME view (such as 3*F1(X)+1 or LN(X)).
If you've found a Root or Extremum then you can do the same thing. If you've just used the FCN menu to find a Slope or Signed Area then you can also retrieve these but the method is a little more involved. Just use the A..Z button to type AREA or SLOPE and hit Enter.
Other values similar to these are stored in the Statistics aplet for you to use. Try this: go the APLET view, START the Statistics aplet, set it to 1VAR and enter a set of data into column C1. Make sure that SYMB is set with C1 ticked. Press the STATS button so that the univariate statistics are displayed. Now change back to the HOME view and press the VARS button. At the bottom of the screen you will see that is ‘ticked’ and that next to it is . Press and move the highlight down to ‘Stat-One’ and ‘Stat-Two’. These contain the list of calculated stats variables. For example, if you move to the right into the ‘Stat-One’ menu you will find all the variables listed in the STATS info screen seen earlier. These can be transferred to the HOME view and used in calculations. Just highlight them and press OK. The name appears in the HOME view and pressing Enter retrieves the value.
Note that what you see when you press the
button depends on which aplet is active.
WARNING: The values stored are those of the last calculation done. If you have more than one column ticked in the SYMB view, resulting in multiple columns in the STATS display then the stored values will be for the last column only. If you wanted to calculate (for example) the mean plus 1.5 standard deviations for 3 different sets of data then you should use the VAR key to enter Mean+1.5*PSDev (Mean has a 'sigma' symbol after it which I can't show on this web page) into the HOME view and evaluate it for the first set of data. Then go back to the Statistics aplet and calculate the STATS for the next set and repeat. (The values are not stored in the VARs until you press STATS.)
If you go to my Utilities page you'll find a software package you can download that lets you send and receive notes, programs and aplets from the calculator to the PC and back. Windows only, I'm afraid! Any view which has SEND and RECV buttons can send either to a computer or to another calculator. You need the cable that came with your calculator - if you've lost it then just go to any electronics shop and ask for a mini-USB cable. They cost about $10 - $20.
See my Help page for a series of instructional pages on what hardware you need, what software and how to install it, and then how to use it all and where to look for aplets. You'll also find pages on programming the calculator which include screen shots.
Just set up the aplet (whichever it is) exactly the way you want it, change into the APLET view and then, while it is highlighted, press SAVE. Give it a name and press ENTER.
The aplet can easily now be transferred to the students' calculators via the infra-red link. Once the class becomes used to this procedure it takes about 2 - 4 minutes for a class of 25 to 30. You send to one student, then the two of you send to two more, then the four of you send to... etc.
You can also save your aplet to a PC if you install the software (see my Utilities page). This means that you can re-use it next year!
Any of those values are now accessible in the HOME view by simply typing the appropriate letter. For example if you change to the HOME view and type T and hit ENTER, you will get the value I quoted above. If you type 3T+2, then you'll get 3 times the value of T plus 2. You can also use this in reverse. If you have done a calculation in the HOME view and you want to use it as the value of one of the variables in an equation in Solve, then just it into the appropriate memory and it will be pre-loaded when you enter the NUM view in Solve.
In the Solve aplet, enter the equation 2*SIN(X)+2=1 in to the SYMB view. Change to PLOT SETUP and set the XRng to 0 to 2pi (using the 3 key to enter pi) and the YRng to -3.1 to 3.2. Enter an XTICK value of pi/4. Now press PLOT. Move the cross-hair close to the first solution (at about X=3.6) and then press NUM. If you now press SOLVE, the calculator will find the nearest solution of 3.665...
Change to the MODES screen and set the NUMBER FORMAT to 'Fraction 6'. Now change to the HOME view and type in X/pi. The answer is 7/6, so the required value is 7pi over 6. Basically you are removing the pi from the answer and giving the calculator the chance to tell you what the associated fraction was.
Now press PLOT, move near the other solution, press NUM and SOLVE, change back to HOME and press ENTER (to repeat the last calculation). This time the solution is 11 pi on 6.
The same method can be used in the Function aplet to find the exact value of intersections. Simply retrieve the value of the last intersection in HOME by typing X in the HOME view and use the same method to isolate the fraction.
Warning! Don't forget to change out of Fraction mode when you finish! If you have put the calculator into Fraction mode then it is going to give you a fractional answer even if the value you gave it was never meant to be one! If you get a fraction like 113/457 then you might suspect that there is a problem. See "How does the Fraction mode work?"
Try this. Use MODES to change into 'Fraction 4' mode. Now go into HOME and type 0.33 and ENTER. You should find that it converts 0.33 into 33/100. Now try the same with 0.333333 This time you will find that it gives you 1/3. Why the difference?
The makers of the calculator have taken a very different approach. Once you select Fraction mode, all numbers become fractions - even decimals. If you are only going to be using fractions from that point on, then this will not cause a problem as long as you bear the following two points in mind….
For example, a setting in the MODES view of....
Basically, the value of ‘n’ in ‘Fraction n’ affects the degree of precision used in converting the decimal to a fraction. This can be useful if you understand what is happening. For example, a setting of Fraction 4 produces a strange (but actually fairly accurate) result for 0.667, while changing to a setting of Fraction 2 will give a result of 2/3. In other words, what makes this approach taken by the calculator useful is that it is often capable of producing results which may be strictly less accurate but are probably closer to what was intended by the 0.667 in the first place.
If you are wanting to use this facility to convert decimals to fractions, here are some tips…
Forgetting the current setting of Fraction can produce some unfortunate effects. For example, at Fraction 2, the value of 123.456 becomes 123, with the 0.456 dropped entirely!
This need for a correct setting of Fraction extends even to working purely with fractions. For example a setting of 'Fraction 4' will correctly result in 1/3 + 4/5 = 17/15. If you use a setting of only Fraction 2 to perform this, you will find to your amazement that 1/3 + 4/5 = 8/7 ! The reason is that the 1/3 and 4/5 were converted to decimals and added to give 1.133333…. This was converted back to a fraction (needing to match only to 2 sig. fig.) to give 8/7 (which is 1.1428..).
In conclusion, while it is not at all suggested that you dismiss the use of the Fraction format, it is important that you understand and remember its limitations. See an earlier question regarding using fraction mode for exact trig values.
This affects the POLYROOT function too. If you use POLYROOT to solve the quadratic equation of x^2+4x+5=0, which does not cross the x axis (try graphing it!) you will find that it gives the roots as complex numbers. They are NOT (x,y) points on the x, y axes! Don't use them - just write "No real solution".
ie.POLYROOT([1,4,5]) gives [(-2,1),(-2,-1)]
Another similar problem is with the inverse trig functions. Since sine and
cosine have ranges of -1 to 1, there should be no answer to ASIN(1.2). However,
the calculator will return a complex answer.
Sam McHarg (Denmark SHS, W.A.)
See also, a detailed paper on teaching Calculus concepts using the HP. This includes further information on problems with limits.
Note: The ON+SK3 is a less drastic version called a soft reset which only does a 'memory sweep' rather than a complete memory clear.
Last modified: 19 Dec 2007 Sitemap Home Contact Me