Getting Error on limit calculation
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farzad
el 2 de Dic. de 2014
Comentada: Star Strider
el 4 de Dic. de 2014
Hi all
I get an error running these lines , but the functions are unknown
could someone tell me what the error is ?
R=1; D11=3;
A(1,:)=[((-R*log®/(2*D11))+R/(4*D11)) R/2 1/R 0]; syms ro;
limit(((-ro*log(ro)/(2*D11))+ro/(4*D11)),ro,0,'right');
syms ro;
limit ( 1/ro,ro, 0, 'right');
A(2,:)=[((-ro*log(ro)/(2*D11))+ro/(4*D11)) ro/2 1/ro 0];
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Star Strider
el 3 de Dic. de 2014
In calculating the limit of ((-ro*log(ro)/(2*D11))+ro/(4*D11)) you are essentially calculating the limit of -ro*log(ro) as ‘ro’ approaches 0 from the right (equating to 0*Inf), and adding it to ‘ro’. Since both terms equate to 0, the limit is 0. I don’t intend to sound critical, but it’s not even necessary to use a symbolic math program to see that.
In your second limit, 1/ro with the same conditions, the limit is +Inf.
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farzad
el 4 de Dic. de 2014
1 comentario
Star Strider
el 4 de Dic. de 2014
My pleasure!
You can certainly use a symbolic solver to do this or almost any problem that has an analytic solution and that is not so large that the solver cannot do it. It is simply obvious that -ro*log(ro) as ‘ro’ approaches zero is going to be zero. So is the second term.
I’m not certain how the Symbolic Math Toolbox calculates its limits (I never looked).
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