solve residue by matlab

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adrian zizo
adrian zizo el 24 de Mzo. de 2015
Comentada: Star Strider el 24 de Mzo. de 2015
plz help me ....
how can I solve this problem by using residue by matlab :
25cos(πz)/((2z+1)^2 (z-2)^2 )
plz help me .. thank u .

Respuestas (2)

Star Strider
Star Strider el 24 de Mzo. de 2015
If you have the Symbolic Math Toolbox, use the partfrac funciton:
syms z
f = 25*cos(pi*z)/((2*z+1)^2 * (z-2)^2 );
pf = partfrac(f, z)
produces:
pf =
cos(pi*z)/(z - 2)^2 - (4*cos(pi*z))/(5*(z - 2)) + (8*cos(pi*z))/(5*(2*z + 1)) + (4*cos(pi*z))/(2*z + 1)^2
  4 comentarios
adrian zizo
adrian zizo el 24 de Mzo. de 2015
but when I enter : syms z
f = 25*cos(pi*z)/((2*z+1)^2 * (z-2)^2 );
pf = partfrac(f, z)
in matlab , matlab give me error ...my matlab version is R2010a
Star Strider
Star Strider el 24 de Mzo. de 2015
According to the online documentation, partfrac was introduced in R2015a, so you wouldn’t have it in R2010a.
I posted the result as ‘pf’ in my Answer, so you have the result of the partfrac operation without having to have the function in your version.

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Konstantinos Sofos
Konstantinos Sofos el 24 de Mzo. de 2015
I would suggest to use L'Hôpital's rule but you could use also the following Adaptive numerical limit (and residue) estimation
  2 comentarios
adrian zizo
adrian zizo el 24 de Mzo. de 2015
I want residue of complex numbers .. plz help me
Konstantinos Sofos
Konstantinos Sofos el 24 de Mzo. de 2015
Editada: Konstantinos Sofos el 24 de Mzo. de 2015
Have a look in the link that i attached you before...
for your given example
f = @(z) 25*cos(pi*z)./((2*z+1).^2 .* (z-2).^2 )

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