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HP Forum Archive 14

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HP 15C Problem
Message #1 Posted by Curtis Quist on 16 Sept 2004, 7:06 p.m.

My 15C will not do trig calculations in degrees. You can set the calculator to degrees or radians, but the calculator only produces results as if in radians. If you set the calculator in degrees, the "rad" sign on the display disappears, but it still calculates in radians. Any thoughts?

Thanks ahead of time,

Curtis Quist

      
Try a reset ...
Message #2 Posted by Karl Schneider on 16 Sept 2004, 9:23 p.m.,
in response to message #1 by Curtis Quist

Interesting; I've never heard of this problem...

Turn the calc off, then press and hold "ON", press and hold "-", then release "ON", then release "-".

You should see "Pr Error" in the display, and everything will be in its default state.

      
Re: HP 15C Problem
Message #3 Posted by Jeff O. on 17 Sept 2004, 7:17 a.m.,
in response to message #1 by Curtis Quist

Is it in complex mode? For trig functions the calculator considers the arguments to be in radians, or expresses results in radians for the inverse functions, when in complex mode regardless of the trig mode set.

            
Re: HP 15C Problem
Message #4 Posted by Curtis Quist on 17 Sept 2004, 11:04 a.m.,
in response to message #3 by Jeff O.

Interesting. I haven't used this calculator for ever. It is at home and I am at work so when I get home I will look at it and see if the C is on, but I think it is. So my question is "How do I get it out of complex mode?"

Curtis

                  
Re: HP 15C Problem
Message #5 Posted by Vieira, Luiz C. (Brazil) on 17 Sept 2004, 11:26 a.m.,
in response to message #4 by Curtis Quist

Hi, Curtis;

to get rid of Complex Mode, clear flag 8:

[g][CF] 8
[CF] is associated to the [5] key. Based on what you wrote, this is most likely to happen. If you take a look at the HP15C Advanced Functions Handbook, p. 68 under Trigonometric Modes, you'll see that
Quote:
Although the trigonometric mode annunciator remains lit in Complex Mode, complex functions are always computed using radians measure.
When converting from rectangular to polar and opposedly in Complex Mode, the trigonometric mode is taken into account. But in this case, the conversions work differently and use only the complex number in X-register.

Hope you can work correctly, now.

Cheers.

Luiz (Brazil)

Edited: 17 Sept 2004, 11:27 a.m.

            
[HP-15C] I'm sure that Jeff is right, but...
Message #6 Posted by Karl Schneider on 17 Sept 2004, 11:56 p.m.,
in response to message #3 by Jeff O.

...my "reset" solution would have worked, too, by clearing complex mode!

A bit of mathematical insight:

The reason that trigonometric functions assume complex-valued arguments in radians (no matter the angular setting) is that hyperbolic functions are used for the solution. Arguments for sinh, cosh, and tanh must be physically dimensionless, which the radian is.

For example:

sin (a + j*b) = (sin a)*(cos j*b) + (cos a)*(sin j*b)
              = (sin a)*(cosh b)  + (cos a)*(j sinh b)
              = (sin a)*(cosh b) + j*(cos a)*(sinh b)

By electical-engineering convention, j = sqrt(-1)

Conversion of a complex-valued argument between rectangular and polar coordinates is different, because hyperbolics are not involved. Luis mentioned that the Advanced Functions Handbook (which is optional at extra cost) documents this operating convention, but it is also documented clearly in the regular Owner's Handbook on p. 121 and pp. 133-134.

-- KS

                  
Re: [HP-15C] A bit more of hyperbolic fcn...
Message #7 Posted by Vieira, Luiz C. (Brazil) on 18 Sept 2004, 1:33 a.m.,
in response to message #6 by Karl Schneider

Hi Karl, guys;

Karl, thanks for mentioning the pages in the HP15C Owner's Handbook. To be honest, I had just the HP15C Owner's Handbook, Portuguese version in hands, and I know page numbers don't match English version, so I decided to mention the ADV FCN Handbook instead. ;-)

A few weeks ago I found this page when searching for Hyperbolic Functions and I kept a copy of it in my HD so I can use in the classroom. I felt its contents are condensed and complete, maybe it can be of help for any others in the need for concise info.

About the 'j' for engineers and 'i' for mathematicians when dealing with complex numbers: I've been curious about this for a long time when I was at the university and I simply forgot about that. Now I read your words and decided to ask again: do you have any idea about the use of different symbols? I used to think it was only to allow a unit being attached to a complex quantity (engineering) instead of using a 'pure' number (math) for that matter, but this is only a reasoning of mine.

Again, this is the kind of thread I like reading and posting about. Cheers.

Luiz (Brazil)

Edited: 18 Sept 2004, 1:40 a.m.

                        
"i" vs. "j"
Message #8 Posted by Karl Schneider on 18 Sept 2004, 2:41 a.m.,
in response to message #7 by Vieira, Luiz C. (Brazil)

Luiz --

Sorry for the brain-lapse misspelling in my last post...

Thanks for providing the link to Mathematica's pages, which are good refernces. Valentin Albillo often links to them in his posts here.

"j" is used in EE to denote the base of imaginary numbers because "i" and "I" are conventionally used for electrical current. "j" stands out a little better from numerals, too.

-- KS

                              
Re: "i" vs. "j"
Message #9 Posted by Vieira, Luiz C. (Brazil) on 18 Sept 2004, 4:05 a.m.,
in response to message #8 by Karl Schneider

Hi Karl, folks;

I'm scratching the top of my head now and thinking: what an obvious reason... Thank you for taking your time to answer. You see, I'm an Electrical Engineer too, and sometimes I have my own doubts being taken away by obvious answers.

And the 'z' in Luiz is somehow unusual. Luis is most commonly found. (thanks for the politeness)

Cheers.

Luiz (Brazil)

                                    
Re: "i" vs. "j"
Message #10 Posted by Curtis Quist on 20 Sept 2004, 9:38 a.m.,
in response to message #9 by Vieira, Luiz C. (Brazil)

Thanks everyone. That fixed it. A guy in my office wanted to buy this thing from me about 8 years ago. He found the radians problem with it. I really wasn't in the mood to get rid of it. Because of this "radians problem" he didn't buy it. I am glad it was there, because I now still have the calculator. But for many years I didn't bother using it because I thought it didn't work properly, and now it works.

Regards,

Curtis Quist


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