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Understanding the HP 28S XPON function
02-25-2017, 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?
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02-25-2017, 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.

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02-25-2017, 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
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02-25-2017, 03:40 PM (This post was last modified: 02-25-2017 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.
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02-25-2017, 04:40 PM
Post: #5
RE: Understanding the HP 28S XPON function
(02-25-2017 12:43 PM)Werner Wrote:  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 ;-)

The 49G with firmware version 1.19-6 contains a DEGREE function that returns the degree of a polynomial. It's listed in the 49G's built-in 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 427-432), including the following:
  • ALGB
  • ASSUME
  • AUGMENT
  • BASIS
  • C2P
  • CASCMD
  • CHOLESKY
  • CIRC
  • COLLECT
  • CONSTANTS
  • CYCLOTOMIC
  • DEF
  • DEGREE
  • DIAGMAP
  • DISPXY
  • DISTRIB
  • DOMAIN
  • DROITE
  • EXP&LN
  • EXP2HYP
  • EXP2POW
  • EXPLN
  • FDISTRIB
  • GAMMA
  • GBASIS
  • GRAMSCHMIDT
  • GREDUCE
  • HELP
  • HYPERBOLIC
  • IBASIS
  • IMAGE
  • INTEGER
  • ISOM
  • KER
  • LASTARG
  • LOCAL
  • MAIN
  • MATHS
  • MKISOM
  • MODULAR
  • MSLV
  • OLDPRT
  • P2C
  • PLOT
  • PMINI
  • POLYNOMIAL
  • POP
  • POTENTIAL
  • POWEXPAND
  • PUSH
  • RCLVX
  • REWRITE
  • RULES
  • SERIAL
  • SIMPLIFY
  • SREV
  • STORE
  • STOVX
  • STURM
  • STURMAB
  • SYST2MAT
  • TAN2CS2
  • TESTS
  • UNASSIGN
  • UNASSUME
  • UNBIND
  • VPOTENTIAL
--- the commands in Library 256 are not included in the list above, but they were not in the 49G AUG either.

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02-25-2017, 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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