Decimal point before an operation  Printable Version + HP Forums (https://archived.hpcalc.org/museumforum) + Forum: HP Museum Forums (https://archived.hpcalc.org/museumforum/forum1.html) + Forum: Old HP Forum Archives (https://archived.hpcalc.org/museumforum/forum2.html) + Thread: Decimal point before an operation (/thread177931.html) 
Decimal point before an operation  Jim Yohe  01292011 Looking at the HP 50g User's Guide on page 114 it shows that you can input an expression directly without using the equation writer. While in the algebraic operating mode, with every entry of a whole number they also show a keypress of a decimal point before an operation (ie, "x" "+" etc..). When in the equation writer they didn't do this and so it's foreign to me, as I've never had to do that with other HP and TI calculators I've owned. Why was it necessary to add a decimal point before an operation?
Re: Decimal point before an operation  Chris Randle (UK)  01292011 Hi Jim, It's not a decimal point before the operator, it's a decimal point after the number. It's a way of overriding the current exact/approximate mode and explicitly stating that you want an approximate result (a numeric answer) rather than an exact result with integers. You can toggle implicit exact/approximate mode by holding down rightshift and pressing enter. If you're in algebraic mode (ALG displayed in the header) and in exact mode (= displayed in the header), try these:
1 / 2 [ENTER] > '1/2' In the last example, you could have left the decimal point off either the 1 or the 2 and you'd have got the same result. If you had tried the example from page 114 without the trailing decimal points, the calculator would have produced a nonapproximate result, but the EXP() function must produce an approximate result, so the calculate instead asks you to confirm a switch to approximate mode. If the calculator is in exact mode and you want an approximate answer, you can use (rightshift) >NUM
1 / 3 [ENTER] > '1/3' [>NUM] > '.333333333333' Edited: 29 Jan 2011, 3:51 p.m.
Re: Decimal point before an operation  Jim Yohe  01292011 Thank you Chris. I am just reading the PDF of the manual and wasn't aware of approximate vs. exact modes. At least not yet. Still it's a bit confusing since this is a new concept to me with respect to how this calculator has been programmed to work.
Re: Decimal point before an operation  Chris Randle (UK)  01292011 It's a great feature of the calculator, and wellimplemented, IMO. In case you're not familiar with HP triglyphs, "\v/" represents the square root symbol, "\>" a rightarrow, and "\pi" the symbol for pi. In exact mode,
\v/4 > 2 because there's an exact decimal representation of the square root of four. But, because the square roots of two and 20 are irrational,
\v/2 > \v/2 Keeping the square roots there in case a later squaring operation is used. If you knew in advance that you wanted an approximate decimal fraction for the square root of two, you could type:
\v/2. > 1.41421356237 to convert back,
\>Q\pi(ANS(1)) > \v/2 \>Q\pi is available from the catalog menu (CAT) The example on page 114 and the examples I've used assume the calculator is in algebraic mode. I prefer RPN mode, and Tim Wessman has produced an additional guide: "HP 50g Graphic Calculator Quick Start Guide" with all examples in RPN mode. If you haven't seen it, you can download a copy here: HP 50g Graphing Calculator Quick Start Guide Also, if you haven't seen a copy of the Advanced User's Reference Manual, which is definitely worth a look, you can get yourself a copy from here:
HP 50g/49g+/48gII graphing calculator advanced user's reference manual
Re: Decimal point before an operation  Jim Yohe  01292011 Thanks again. I wanted to point out that the second link is broken with a message of, "The page you requested can not be found". Does this happen to now be the "Advanced_Users_Ref_Manual.zip" file you can download from here?:
http://h20000.www2.hp.com/bizsupport/TechSupport/DocumentIndex.jsp?lang=en&cc=us&contentType=SupportManual&docIndexId=64255&prodTypeId=215348&prodSeriesId=3235173&lang=en&cc=us Edited: 29 Jan 2011, 8:14 p.m.
Re: Decimal point before an operation  Chris Randle (UK)  01302011 Sorry about the broken link. Could have sworn it worked when I tried it. But yes, that zip file is the one I meant. The AUM's a great work.
