This calculator is just what I wanted and needed. I have owned top of the line graphing calculators from HP, Casio, Sharp, TI, etc., but overall I like this one almost the best due primarily to its simplicity and ease of use. I like it especially for trips and outside activities when I can do quite useful mathematical explorations that I don't normally have time for at home or in the office with my busy schedule. It was designed by HP and teachers, first and foremost however, as an aid in teaching HIGH SCHOOL students mathematics in a very user-friendly manner.
PROS:
1) It is simple, fairly light and quite fast (75 MHz clock speed), algebraic equation operating system (EOS), but not with HP RPN, but not bad for the money since the hp 39gs units are now on sale for $63.99 compared with $59.99 for the new HP 35s for example which is a great machine, but which is totally outclassed by this much more versatile unit. The hp 39 gs is now about one year in production having replaced the 39G+ with a much better designed keyboard, etc. as described below and has evolved through 3-4 flavors from the original HP 38 of about a decade ago).
2) Very well organized analysis activities using special Aplets with about a dozen available with the unit and many many more on the world wide web (or you can write your own since programming is also available on the 39 gs). These specialized Aplets include analysis of functions, parametric equations, the famous HP solver system, statistics, etc. (with least squares curve fits available for about a dozen types, such as cubic, exponential, power law, logistic or even a user defined type, etc.!). The unit also has about 200 kb of available RAM and about 1 Mb of ROM for the operating system which is a lot more than the more powerful hp 48gII for example.
3) It will supply three types of analysis for every problem, namely a numerical table of values, a graphic plot (only two-dimensional types however) and a symbolic analysis which is only completely possible for the simplest Calculus cases (polynomials and basic trig, logarithmic and hyperbolic functions). Nevertheless, it also does numerical differential and integral Calculus and it can even supply a Taylor series approximation for your functions. It can also display a fine split-screen view (side by side) supplying a table of values as well a plot which is also very useful (with many useful zoom options).
4) It also handles some advanced mathematical functions (including hyperbolics, etc.) and of course can be used to analyze complex numbers, lists and matrices and can even take the square root of negative numbers directly in a very straight forward manner (unlike the HP 35s)!
5) It also allows the user to make detailed notes and sketches and also interfaces very nicely with a PC using the USB cable supplied with the unit for exchanging information. It also has an RS-232 (serial) as well as an infrared transfer option available as well.
6) It comes with a well written and well organized 314 page users manual and with an even more advanced manual available on the supplied CD.
7) It has a new Flash ROM so that the calculator can be electronically updated if new EOS software ROM's are produced by HP without changing out the hardware.
8) Date and time is always available with the on-board clock (using the DISPTIME command)
9) The unit has a totally redesigned keyboard that has quite an excellent feel to it (unlike the fiasco's connected with the HP 49g series for example and even better in my humble opinion than the revered HP 50g now in production for over a year too which I also own). The overall unit seems to be very well made and should last a very long time too. As always, the calculator special self tests are excellent and are triggered by simple keystroke commands. Also, Typing RULES or AMIGOS in "Home" produces two "HP easter eggs" of people who were involved in the design and production of this great system.
10) It has a completely scrollable operations history in HOME (unlimited within the available RAM memory and also easy to erase when extra memory is needed) that is very easy to manipulate by using the Copy command to recall previously evaluated expressions in order to perform quick "what-if" analysis, etc.
11) It is also very intuitive to operate in my opinion even without HP RPN. It is a great start to get students and teachers interested in doing more math and science too which is a very good thing considering recent trends in North America.
CONS
1) The batteries only last 65 hours according to HP. I can't confirm this fact as of yet, but it uses 4 AAA batteries as well as a common Lithium battery to be used as a backup while changing the main batteries.
2) It is quite thick in comparison to other such calculators and in spite of the supplied high quality slide-on cover (a maximum total 1.22 inches thick with the cover on for protection), HP should have supplied a good case for further protection as has been its standard for many other of its calculators (including the HP 35s). Why just imitate the other manufacturers with a slide-on cover for its only protection? HP has always gone its own way in this field considering how few people really understand or actively use RPN logic every day (which I have previously always preferred for many years now). Most of us now have easily accessible computers and compilers to do most computing tasks. I usually use a calculator at work only to carefully check intricate computer calculations, but when I do I want it to be simple and easy to use, especially since I don't use it every day.
3) It will not analyze ordinary differential equations as the more advanced calculators can now readily do. Also, the statistical applet correlation coefficient provided is only for a linear curve fit (regardless of the fit assumed). The relative error is provided instead for both the linear as well as for any of the other curve fit options.
4) Hopefully its sister calculator, the HP 40gs (with a full HP Computer Algebra System-CAS) for UNIVERSITY LEVEL will also be released in North America soon. HP has recently combined efforts (as of early May, 2007) with a company in Oregon to use the 39GS and 40GS for routine laboratory measurements at high schools and at universities in the very near future. HP39GS Graphing Calculator - Calculator - Scientific Calculator - Hp Calculator - Graphing'
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