Program for finding roots and selecting one
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03-09-2016, 01:40 AM
Post: #1
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Program for finding roots and selecting one
I am making a program an at some point i need the program to:
1) Find the roots of a cubic polinomi 2) The roots are always going to be 2 complex and 1 real ( cause of the physics behind). And i want the program to select the real one and define it as "Z" 3) Now that Z is define as one number ( the real root out of the three possible) it can continuo with my calculations. I have the doubt that if I calculate the roots through Cas.function('expresion'), the three routs will come out as a vector, list, matrix or what? |
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03-09-2016, 02:43 AM
Post: #2
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RE: Program for finding roots and selecting one
Is this a PRIME specific question? otherwise, HP calculator programs for the solution of cubic equations go back to at least the HP-65 with program #7 in MATH PAC 1.
Kahan has two source locations on the topic: a. To Solve a Real Cubic Equation found at Cubic b. To Solve A Real Cubic Equation found at AD a206859 as well as Analytic Solution of Quartic & Cubic Polynomials by A J Helou, BCE, M.Sc., Ph.D. BEST! SlideRule |
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03-09-2016, 04:26 AM
Post: #3
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RE: Program for finding roots and selecting one
(03-09-2016 02:43 AM)SlideRule Wrote: Is this a PRIME specific question? otherwise, HP calculator programs for the solution of cubic equations go back to at least the HP-65 with program #7 in MATH PAC 1. Thank you very much, and yes, its for the HP PRIME. I was thinking to use the CAS.function('expression') to find the roots instead of programming a cubic root finder. My real problem is which command should I use in the programm so that when the CAS.function gives the 3 roots, the programm choses the only real root out of the 3 roots ( 2 complex and 1 real.) and then define that real root as the valua of "Z" so it follows its calculations. |
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03-09-2016, 08:38 AM
Post: #4
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RE: Program for finding roots and selecting one
(03-09-2016 04:26 AM)Eugenio Wrote: I was thinking to use the CAS.function('expression') to find the roots instead of programming a cubic root finder. My real problem is which command should I use in the programm so that when the CAS.function gives the 3 roots, the programm choses the only real root out of the 3 roots ( 2 complex and 1 real.) and then define that real root as the valua of "Z" so it follows its calculations. This should work for you: Code: EXPORT RealRoot(poly) |
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03-10-2016, 04:57 AM
Post: #5
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RE: Program for finding roots and selecting one
(03-09-2016 08:38 AM)Didier Lachieze Wrote:(03-09-2016 04:26 AM)Eugenio Wrote: I was thinking to use the CAS.function('expression') to find the roots instead of programming a cubic root finder. My real problem is which command should I use in the programm so that when the CAS.function gives the 3 roots, the programm choses the only real root out of the 3 roots ( 2 complex and 1 real.) and then define that real root as the valua of "Z" so it follows its calculations. Thank you so much for your help, it has been really helpfull. It works and suits perfectly |
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