Understanding the HP 28S XPON function

02252017, 12:21 AM
Post: #1




Understanding the HP 28S XPON function
I guess I don't quite understand the usefulness of the XPON function on the HP 28S for symbolic expressions. I tried to evaluate the expression XPON("X^3") using >NUM but it returns the error: Undefined Name. How does one, for example, determine the degree of a polynomial expression?


02252017, 06:40 AM
Post: #2




RE: Understanding the HP 28S XPON function
XPON is only for real numbers, not algebraic objects. HP 28S RPL does not contain a command that returns the degree of a polynomial. The DEGREE command which does that was introduced into RPL later, in the HP 48G.
<0ɸ0> Joe 

02252017, 12:43 PM
Post: #3




RE: Understanding the HP 28S XPON function
Probably the 50G, Joe. The 49G AUG does not know DEGREE.
(I have only a 48 and a 49, and I never heard of it  but that's not a reliable reference ;) Cheers, Werner 

02252017, 03:40 PM
(This post was last modified: 02252017 04:00 PM by mbrethen.)
Post: #4




RE: Understanding the HP 28S XPON function
I wonder if this can be successfully programmed for the 28s? One thought I had is to perform successive differentiation until you end up with a constant? A loop counter could keep track of the number.
Another idea is to evaluate the polynomial using Horner's method (PVAL in the Math Applications reference) and then SIZE the nested list. 

02252017, 04:40 PM
Post: #5




RE: Understanding the HP 28S XPON function
(02252017 12:43 PM)Werner Wrote: Probably the 50G, Joe. The 49G AUG does not know DEGREE. The 49G with firmware version 1.196 contains a DEGREE function that returns the degree of a polynomial. It's listed in the 49G's builtin CATALOG, and it has a help screen. The 49G AUG is unfortunately missing an astounding number of 49G commands (at least they are missing from its Command Index on pages 427432), including the following:
<0ɸ0> Joe 

02252017, 09:25 PM
Post: #6




RE: Understanding the HP 28S XPON function
I stand corrected ;)
At least it's the 49, not the 48 ;) Werner 

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