solve residue by matlab
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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 .
回答（2 个）
Star Strider
2015-3-24
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 个评论
adrian zizo
2015-3-24
Star Strider
2015-3-24
The ‘pf’ expression provides you with the partial fraction evaluated at exactly those values. If you substitute them in for ‘z’ in that expression, you will get an infinite result for each, as expected.
adrian zizo
2015-3-24
Star Strider
2015-3-24
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.
Konstantinos Sofos
2015-3-24
0 个投票
I would suggest to use L'Hôpital's rule but you could use also the following Adaptive numerical limit (and residue) estimation
2 个评论
adrian zizo
2015-3-24
Konstantinos Sofos
2015-3-24
编辑：Konstantinos Sofos
2015-3-24
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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