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HP Forum Archive 17

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Message #1 Posted by deleted on 10 Oct 2007, 9:52 a.m.

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Re: HP 35s problem with complex numbers.
Message #2 Posted by Gene Wright on 10 Oct 2007, 2:42 p.m.,
in response to message #1 by deleted

How are you trying to enter such a complex number?

I know you can press 3 i 4 and get that complex number on the stack, but what are you pressing to create a complex number using a variable or a constant?

Give us a specific example of what keys you're pressing (or what equation you're trying) and that will help.

            
Re: HP 35s problem with complex numbers.
Message #3 Posted by Ike on 10 Oct 2007, 3:05 p.m.,
in response to message #2 by Gene Wright

I wanted to try Euler's equation:

e^(i(pi)) + 1 = 0

For the exponent if I enter "0 i 3.14" where I manually enter an estimate of pi, I'm OK

If I enter "0 i shift pi" I am left with pi in the real portion of the number with no imaginary component and who know what in rectangular form in the Y register above it. This is very perplexing.

So I tried storing pi in the "a" register and tried: "0 i RCL a" and I get the same kind of nonsensical result. It sure is frustrating.

Edited: 10 Oct 2007, 3:07 p.m.

                  
Re: HP 35s problem with complex numbers.
Message #4 Posted by Gene Wright on 10 Oct 2007, 3:48 p.m.,
in response to message #3 by Ike

The reason is because you cannot build complex numbers from values in registers or constants in the manner you are trying.

You can see this in a program.

In program mode, press EQN to turn on equation mode and type:

RCL B then i then 2

Now leave program mode and single-step that program line. You get a syntax error.

Try the approach shown in the next posting.

Edited: 10 Oct 2007, 4:07 p.m. after one or more responses were posted

                        
Re: HP 35s problem with complex numbers.
Message #5 Posted by Ike on 10 Oct 2007, 4:06 p.m.,
in response to message #4 by Gene Wright

Gene,

Thanks for your thoughtful response even though it isn't what I wanted to hear! It's too bad a complex variable cannot be constructed from constants or a register - why should the calculator care where the number comes from?

Oh well, on to the next problem like world peace or some such thing.

Cheers, Ike

                  
Re: HP 35s problem with complex numbers.
Message #6 Posted by Egan Ford on 10 Oct 2007, 3:58 p.m.,
in response to message #3 by Ike

Try:

PI
i
*
e^x
1
+
With a reg:
i
RCL* P
e^x
1
+
                        
Re: HP 35s problem with complex numbers.
Message #7 Posted by Ike on 10 Oct 2007, 4:10 p.m.,
in response to message #6 by Egan Ford

Egan,

I will try your steps when I get home for there is where I left my HP35s. I will certainly let you know the outcome unless someone has a 35s with them now and can try your procedure.

Thanks, Ike

                  
Re: HP 35s problem with complex numbers.
Message #8 Posted by Karl Schneider on 10 Oct 2007, 10:31 p.m.,
in response to message #3 by Ike

Ike --

Egan Ford's previous response is correct. The reason for the seemingly-inconsistent behavior is that hitting the pi key terminates data entry and pushes pi onto the stack. A previously-entered "i" then becomes a complete number, represented as "0i1" (0 + i1). Multiplying pi by "i" in either order produces the value you wanted.

I have made detailed suggestions to HP's calculator team for improving the complex-number functionality, and will continue to follow up on them. Help may be on the way, if you're willing to wait a number of months.

-- KS

                        
Re: HP 35s problem with complex numbers.
Message #9 Posted by Ike on 10 Oct 2007, 11:28 p.m.,
in response to message #8 by Karl Schneider

Karl,

Yes, Eagan is correct especially in the first solution. I had a bit more problem with the second but I'm not going to worry about it anymore. The bottom line is that now with the help from you folks I have something I can live with - thanks!

Now get those HP folks in line!

Cheers! Ike

                              
Re: HP 35s problem with complex numbers.
Message #10 Posted by Egan Ford on 10 Oct 2007, 11:38 p.m.,
in response to message #9 by Ike

For the 2nd:

1.  Put a value in a register, e.g. A
2.  Then type:

i RCL* A i.e. RCL, then x (times), then A, aka recall arithmetic.

Or to make it easy:
i
RCL A
*
Both will build you a complex number from registers. For A+iB:
number
STO A
number
STO B

i RCL* B RCL+ A

OR

i RCL B * RCL A +

                        
Re: HP 35s problem with complex numbers.
Message #11 Posted by Trent Moseley on 11 Oct 2007, 10:06 p.m.,
in response to message #8 by Karl Schneider

Karl - I'm numb with this stuff. Having solved all complex problems with the 42s why did HP need to reinvent the wheel?

tm

                              
Re: HP 35s problem with complex numbers.
Message #12 Posted by DaveJ on 11 Oct 2007, 10:54 p.m.,
in response to message #11 by Trent Moseley

Quote:
Karl - I'm numb with this stuff. Having solved all complex problems with the 42s why did HP need to reinvent the wheel?

Two reasons: 1) Companies are ruled by marketing. 2) There is no such thing as one tool for every job.

Dave.

                                    
Re: HP 35s problem with complex numbers.
Message #13 Posted by Trent Moseley on 11 Oct 2007, 11:24 p.m.,
in response to message #12 by DaveJ

Dave-

You missed my point.

tm

                                          
Re: HP 35s problem with complex numbers.
Message #14 Posted by DaveJ on 11 Oct 2007, 11:59 p.m.,
in response to message #13 by Trent Moseley

Quote:
You missed my point.

Ok, sorry, what was your point?

Dave.

                              
Re: HP 35s problem with complex numbers.
Message #15 Posted by Karl Schneider on 12 Oct 2007, 1:04 a.m.,
in response to message #11 by Trent Moseley

Hi, Trent --

Quote:
Having solved all complex problems with the 42s why did HP need to reinvent the wheel?

Well, I can't fully concur on that point. I have yet to see a calculator from any manufacturer having ideal complex-number functionality, but certainly the HP-42S is among the best. Its display of complex numbers is perfect, but the HP-42S lacks the following:

  • Direct, one-step entry of complex numbers in rectangular or polar form in either "mode" (as the HP-35s has)
  • A menu of complex-number functions (as the HP-28C/S has)
  • Mixed-mode display of complex numbers with most-reasonable result format (Simple and straightforward, but I've never seen it done -- by HP or by TI or Casio in the models I've examined)

Details will follow, hopefully within a week. Here's a sample:

User-friendly complex numbers

-- KS

      
i^2 = invalid data in one case
Message #16 Posted by DavidB on 11 Oct 2007, 1:10 a.m.,
in response to message #1 by deleted

In mathematics, the square of imaginary unit i is -1. If I enter the imaginary number 0i1 and then take the square of it (x^2), the HP 35s displays "INVALID DATA." The same happens when I enter any complex number and take the square of it using the x^2 key on the calculator.

If I enter the following, as shown in manual, p. 9-5:

1i1 ENTER 2 (positive 2 here) y^x

The result is 0i2, since (1 + i)^2 = 1^2 + i + i + i^2 = 1 + 2i -1 = 0 + 2i

So, in one way, the 35s does compute i^2. But just using x^2 will not work. If I enter:

i 1 ENTER 2 y^x

I get the result as -1i0 (or -1 + 0i). I originally thought the 35s did not compute i^2 at all, but it does. As noted in the manual, you can y^x to compute powers of a complex number.

Cheers!

David Bailey

Edited: 11 Oct 2007, 1:51 a.m.


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