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How to compute the value of symbolic expressions in HP-50g?
Message #1 Posted by Luca on 16 Aug 2009, 3:37 p.m.

I realize this must be a very simple question, but how do I evaluate expressions containing symbols? Suppose you have a simple expression, for instance: 

X*(M-1)
-------
X*(M+1)
I would like to press on a key that did:
  • Prompts for all the values of the symbols, such as X, M in the example, showing the previous value if any.
  • Returns the value of the expression.
This seems to be rather basic functionality, similar to the equation mode, so I am sure that there is a way to do it... but which way? Many thanks... as you can see, I am a beginner with my 50g.

Luca

      
Re: How to compute the value of symbolic expressions in HP-50g?
Message #2 Posted by Hal Bitton in Boise on 16 Aug 2009, 8:16 p.m.,
in response to message #1 by Luca

No problem, Luca,
Just use the equation solver thusly:

Assuming your equation is on the stack level 1:
...copy it (up arrow and put the pointer on level 1, right shift, copy, enter)
...open the equation solver (right shift, num.slv, option 1 (which is Solve equation).
...with the Eq field highlighted, hit paste (right shift, paste) and enter. (note; if your equation is stored in a variable, just hit CHOOSE and navigate to your variable)
...The application will put the equation into the field, and it's variables will appear below. Select any variable and put a value into it (by keying in the number and hitting enter). Highlight the variable you want to solve for and hit solve (f6 softkey). You can put an initial guess into the variable you want to solve for prior to solving if you want to. You can change the values and or solve for any of the variables you want to.
...note that when you exit the solver application, the solution(s) found by the equation solver have automatically been put on the stack as a tagged object(s), which can then be used in subsequent calculations.
best regards,
hal

            
Re: How to compute the value of symbolic expressions in HP-50g?
Message #3 Posted by Luca on 17 Aug 2009, 2:36 a.m.,
in response to message #2 by Hal Bitton in Boise

Thanks! This helps.

I just wish that the numeric solver would display the value it computes when I assign values to the variables and press EXPR= , rather than just leaving the value on the stack.

I did not know I had to use the solver even for evaluating an expression, but I see that it works well. Thanks!

Luca

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