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HP Forum Archive 19

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Pi wrong?
Message #1 Posted by Bruce Bergman on 30 Mar 2010, 1:31 p.m.

So, I've been sitting here on hold with BofA for what must seem like hours, and I'm gazing at my HP calculator poster, looking at the various models. Very pretty. ;-)

As I glance at the HP-10bii model ("R2D2"), I see the value of Pi in the display. 3.1415926545.

Wait. 545? I always knew it as 3.1415926535.

My HP-97 says 3.141592654 (using DISP), so, okay, it rounded up.

My HP-30b says 3.14159265359 (gotta love the extra digit).

I don't have an HP-10bii handy, but that value in the display, on the poster, appears to be wrong. Was it just typed in or actually displayed wrong on that unit?

Inquiring (bored) minds want to know.

thanks, bruce

      
Re: Pi wrong?
Message #2 Posted by Katie Wasserman on 30 Mar 2010, 1:40 p.m.,
in response to message #1 by Bruce Bergman

The 10bii doens't have a pi key nor trig functions nor other obvious way to calculate pi so it almost certainly was typed in wrong.

-Katie

            
Re: Pi wrong?
Message #3 Posted by hpnut on 30 Mar 2010, 3:04 p.m.,
in response to message #2 by Katie Wasserman

IIRC pi=22/7

so any calculator ought to be able to display pi

                  
(deleted post)
Message #4 Posted by deleted on 30 Mar 2010, 3:08 p.m.,
in response to message #3 by hpnut

This Message was deleted. This empty message preserves the threading when a post with followup(s) is deleted. If all followups have been removed, the original poster may delete this post again to make this placeholder disappear.

                        
Re: Pi wrong?
Message #5 Posted by Walter B on 30 Mar 2010, 4:06 p.m.,
in response to message #4 by deleted

Sufficient for most order-of-magnitude guessing - even 3.0 would do d;-)

                        
Re: Pi wrong?
Message #6 Posted by Mike Morrow on 31 Mar 2010, 8:03 a.m.,
in response to message #4 by deleted

Quote:
Not true...Pi is an irrational number.

Not much of a sense for humor or sarcasm, eh?

                  
Re: Pi wrong?
Message #7 Posted by Garth Wilson on 30 Mar 2010, 5:49 p.m.,
in response to message #3 by hpnut

22/7 is off by about +4.0E-4.
245/78 is off by about -1.8E-4 (not a whole lot better).
355/113 is off by about +8.5E-8.
65298/20785 is off by about -5.1E-8.
93343/29712 is off by about -9.9E-9.
For 16-bit scaled-integer work with 32-bit intermediate results, 355/113 is usually used as it is quite accurate and you have to go to much higher numbers, all the way to 62298/20785, to get any better, and even that doesn't bring much improvement.

Edited: 30 Mar 2010, 5:50 p.m.

      
Re: Pi wrong?
Message #8 Posted by Chuck on 30 Mar 2010, 4:07 p.m.,
in response to message #1 by Bruce Bergman

That's pi for the statisticians who only ever need to be 95% correct. ;)

            
Re: Pi wrong?
Message #9 Posted by Walter B on 30 Mar 2010, 4:10 p.m.,
in response to message #8 by Chuck

95% are 2 significant digits only ;) Please see my post above.

      
Re: Pi wrong?
Message #10 Posted by Didier Lachieze on 30 Mar 2010, 6:06 p.m.,
in response to message #1 by Bruce Bergman

My Sharp EL-5001 shows Pi as 3.141592653.

Here with a Sharp EL-515 showing Pi as 3.141592654:

Btw the EL-5001 is a pretty strange beast with mechanical/preprogrammed soft keys ~10 years before the HP-18C/28C.

Edited: 30 Mar 2010, 6:12 p.m.

      
Re: Pi wrong?
Message #11 Posted by Martin Pinckney on 30 Mar 2010, 8:55 p.m.,
in response to message #1 by Bruce Bergman

Did anyone stop to think how nutty it is for grown men (woman) to be bantering back and forth for hours on such a subject?

Pi are round. Cornbread are square.

            
Re: Pi wrong?
Message #12 Posted by bill platt on 30 Mar 2010, 9:32 p.m.,
in response to message #11 by Martin Pinckney

We might think of that, but put it out of our mind.

This is one of those special places where we get to eat our pi and our square roots too.

                  
Re: Pi wrong?
Message #13 Posted by Chuck on 30 Mar 2010, 11:53 p.m.,
in response to message #12 by bill platt

This reminds me of Donald walking through the forest of square roots in Donald In Mathmagic Land. Priceless!!

      
Re: Pi wrong?
Message #14 Posted by db (martinez, ca.) on 30 Mar 2010, 11:53 p.m.,
in response to message #1 by Bruce Bergman

a real bad slice of pi=
http://www.msdsite.com/photopost/showphoto.php?photo=290&cat=534


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