problem using 'Solve' (return only 1 solution)
7 visualizaciones (últimos 30 días)
Mostrar comentarios más antiguos
Marco Picillo
el 22 de Mayo de 2021
Comentada: Marco Picillo
el 23 de Mayo de 2021
Hello,
I have a problem using solve for a symbolic expression (i'm using Matlab 2019a). I have a 3rd degree polynomial symbolic expression, and i want to find the roots.
I used:
[soluzione]=vpa(solve(equazione_gamma,CL,'Real',true))
and matlab returns:
soluzione =
0.047620242010553458040855966913202
But i expected 3 real solutions, in fact i tried using 'roots' and the solutions are:
p=[0.638 0.360 -0.860988 0.0401];
roots(p)
ans =
-1.4950e+00
8.8318e-01
4.7602e-02
(i approximated the coefficients). Seems that Matlab returns me only the last solution. What's the problem?
Thank you!
0 comentarios
Respuesta aceptada
Andreas Apostolatos
el 22 de Mayo de 2021
Hi Marco,
It is not clear how you define expression 'equazione_gamma', but by reverse engineering your call to function 'roots', I believe that you define 'equazione_gamma' as '0.638*CL^3 + 0.360*CL^2 - 0.860988*CL + 0.0401' where 'CL' is a symbolic variable.
This way, the following script provides all three expected solutions in both MATLAB R2019a (both in general release and in Update 9) and MATLAB R2021a, namely,
syms CL;
equazione_gamma = 0.638*CL^3 + 0.360*CL^2 - 0.860988*CL + 0.0401;
[soluzione] = vpa(solve(equazione_gamma,CL,'Real',true))
soluzione =
0.047601767084402707714683600900841
0.8831762954368845400443443535789
-1.4950413854052997869439809325362
I hope this information helps.
Kind regards,
Andreas
Más respuestas (0)
Ver también
Categorías
Más información sobre Number Theory en Help Center y File Exchange.
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!