Solution of dsolve with varible f which is not declared with syms

Question

Vladan Radulovic 2012-10-8

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https://ww2.mathworks.cn/matlabcentral/answers/50165-solution-of-dsolve-with-varible-f-which-is-not-declared-with-syms

编辑： Walter Roberson 2015-7-8

I am trying to get solution of the differential equation of second order with code given bellow:

clc

clear

syms L C R E w t uc

u=dsolve('L*C*D2uc+R*C*Duc+uc-E*cos(w*t)=0','uc(0)=E','Duc(0)=0','t');

MATLAB 7.0 gives me solution in which exists variable "f". As it can be seen, this variable has not been declared. Consequently, If I want to implement subs function, I can not substitute all variables.

What seems to be problem and please, what would be solution?

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Answer 1

RahulTandon 2015-7-7

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https://ww2.mathworks.cn/matlabcentral/answers/50165-solution-of-dsolve-with-varible-f-which-is-not-declared-with-syms#answer_185284

编辑：Walter Roberson 2015-7-8

%% Section 1
% IT WORKS, HERE IS THE SOLUTION
clc;
syms L C R E w t uc CLEAR;
u=dsolve('L*C*D2uc+R*C*Duc+uc-E*cos(w*t)==0','uc(0)=E','Duc(0)=0','t');
% THERE IS NO F IN THE SOLUTION
% BUT IT IS A LONG AND COMPLEX ONE