Product Series and Limit Expressions on the 50G

[Matt Agajanian]

Although the 50G does have summation series, definite and indefinite integral entry directly in the Equation Writer, how do I input a Product Series expression into the 50G?

Next, how do I enter a Limit expression in the 50G Equation Writer?

Thanks

[Gilles Carpentier]

For 'limit' with EWQ, I do :

Shift Calc Limit LIM
then enter the equation and the limit in the second argument in the form X=0

It's unclear in the doc but

X=0+0
X=0-0

means right and left limits

However the input is not in '2D'... It's become '2D' after ENTER and you can edit in 2D after that. Perhaps there is another way ?

[Matt Agajanian]

A little help, please. How would asample expression be written in RPN mode?

Thamk you

NEVER MIND!

I got the idea.

So, how do I enter a product series (upper case Greek Pi) expression?

Edited: 2 Sept 2013, 3:20 p.m.

[Gerson W. Barbosa]

There is no PI operator, but you can use SIGMA, LN and EXP together. Let's say you want the product of the first ten natural numbers (a.k.a. 10!), or

'PI(n=1,10,n)'

But the HP 50g lacks PI, as we know. No problem, do that instead:

'EXP(SIGMA(n=1,10,LN(n)))'

EVAL

You'll get 3628800.00009. Well, those extra 0.00009 are a small price to pay :-)

HTH,

Gerson.

Edited: 2 Sept 2013, 3:38 p.m.

[Matt Agajanian]

So, are you saying, in the last argument (from your example, 'LN(n)', justl replace the argument n with my math expression?

But, if the expression, n, produces a negative value through the range of the series, taking LN(expression) will result in an error condition. Wouldn't it? Or, since the 50G will handle complex results, the calculation of the Product Series will calculate thoroughly?

[Gerson W. Barbosa]

Quote:

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But, if the expression, n, produces a negative value through the range of the series, taking LN(expression) will result in an error condition.

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Yes, that's a concern. This method won't work for all cases, still a few of them will be easily handled. For instance, if all terms have negative value, just make them positive then change the sign of the result if the numbers of terms is odd.

[Matt Agajanian]

Okie doke!

Thanks.

[Bunuel66]

May be computing with absolute value will solve the problem...and then finding the final sign by hand....

[Matt Agajanian]

There's got to be a better way with such a feature- and function-loaded calculator.

[Thomas Ritschel]

Outside the equation writer one could use a combination of SEQ and PILIST (from the MTH/LIST menu). This would also work for negative members of the series.

For example for odd integers from n=-5 to n=5:

n

n

-5

5

2

SEQ

You'll get a list:

{-5 -3 -1 1 3 5}

PILIST

yields -225.

In ALG mode one could combine the two statements into just one line. However I haven't found a way to enter this in RPN mode (apart from temporarily switching to and from ALG mode).

Edited: 2 Sept 2013, 5:17 p.m.

[Matt Agajanian]

Well, that sounda like a good fix. Besides, it feels and sounds like that programming routine gets my RPN programming juices fired up. Yeah, after taking a break and looking at this in a relaxed mood, this idea (and I wouldn't mind seeing other methods) makes for a good alternative.

[Matt Agajanian]

Actually, to keep this an entirely RPN item, you could do what I just tried and just put that PiList command into the program as the last instruction. Or were you trying for a stack-based function instead of a program?

Edited: 2 Sept 2013, 7:38 p.m.

[Thomas Ritschel]

Quote:

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Or were you trying for a stack-based function instead of a program?

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Yes, I was trying for a stack-based function (equation). Within a program it is no problem to put the PiList directly after the SEQ statement...

[Simone Cerica]

Quote:

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Although the 50G does have summation series, definite and indefinite integral entry directly in the Equation Writer, how do I input a Product Series expression into the 50G?

Next, how do I enter a Limit expression in the 50G Equation Writer?

Thanks

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You must read "PI (Product) function for 48/49/50" of John H Meyers on comp.sys.hp48

best regards,
Simone Cerica