How to use syms in multiple variable?
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I wrote a code to integrate a function with respect to time, but it gives an error message. I am not able to identify the mistake in writing the code. Please help.
syms x1 x2 x3 t
c1(x1,t)=5*x1^2*t+5*x1+5;
c2(x2,t)=6*x2^2*t+6*x2+6;
c3(x3,t)=7*x3^2*t+7*x3+7;
chi1=diff(c1,x1);
chi2=diff(c2,x2);
chi3=diff(c3,x3);
y1_dot=(-k1*sign(+1*(chi2-chi1))*abs(+1*(chi2-chi1))^mu-k2*sign(+1*(chi2-chi1))*abs(+1*(chi2-chi1))^nu);
y2_dot=(-k1*sign(+1*(chi1-chi2)+1*(chi3-chi2))*abs(+1*(chi1-chi2)+1*(chi3-chi2))^mu-k2*sign(+1*(chi1-chi2)+1*(chi3-chi2))*abs(+1*(chi1-chi2)+1*(chi3-chi2))^nu);
y3_dot=(-k1*sign(+1*(chi2-chi3))*abs(+1*(chi2-chi3))^mu-k2*sign(+1*(chi2-chi3))*abs(+1*(chi2-chi3))^nu);
y1=int(y1_dot,t);
y2=int(y2_dot,t);
y3=int(y3_dot,t);
3 个评论
Steven Lord
2022-4-7
Please show us the the full and exact text of the error and/or warning messages (all the text displayed in red and/or orange in the Command Window) that you receive when running that code. This information may help us determine why the code throws that error or issues that warning.
Walter Roberson
2022-4-7
mu and k variables are not defined
John D'Errico
2023-2-27
Please don't use a flag to say your own question is not clear. If it is not clear, then make it clear.
回答（1 个）
Torsten
2022-4-7
This code does not throw an error, but I don't know whether it will succeed to find an antiderivative for your expressions.
syms x1 x2 x3 t k1 k2 mu nu
c1=5*x1^2*t+5*x1+5;
c2=6*x2^2*t+6*x2+6;
c3=7*x3^2*t+7*x3+7;
chi1=diff(c1,x1);
chi2=diff(c2,x2);
chi3=diff(c3,x3);
y1_dot=(-k1*sign(+1*(chi2-chi1))*abs(+1*(chi2-chi1))^mu-k2*sign(+1*(chi2-chi1))*abs(+1*(chi2-chi1))^nu);
y2_dot=(-k1*sign(+1*(chi1-chi2)+1*(chi3-chi2))*abs(+1*(chi1-chi2)+1*(chi3-chi2))^mu-k2*sign(+1*(chi1-chi2)+1*(chi3-chi2))*abs(+1*(chi1-chi2)+1*(chi3-chi2))^nu);
y3_dot=(-k1*sign(+1*(chi2-chi3))*abs(+1*(chi2-chi3))^mu-k2*sign(+1*(chi2-chi3))*abs(+1*(chi2-chi3))^nu);
y1=int(y1_dot,t);
y2=int(y2_dot,t);
y3=int(y3_dot,t);
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2023-2-27
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