# dsolve error (simultaneous differential equations)

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Seungwon Lee il 18 Mag 2020
Commentato: Seungwon Lee il 18 Mag 2020
clear all
close
clc
m = 10;
k = 1000;
u0 = 0.01;
syms y1 y2
f=dsolve('m*D2y1+2*k*y1-k*y2==0,m*D2y2-k*y1+2k*y2==0','y1(0)==0,Dy1(0)==0,Dy2(0)==0,y2(0)==0.01');
figure
ezplot(f,[0 100]);
I want to solve simultaneous differential equation but i have a problem solving it.
Can someone help me find whats causing error?
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### Risposta accettata

Sulaymon Eshkabilov il 18 Mag 2020
clear all
close
clc
m = 10;
k = 1000;
u0 = 0.01;
syms y1(t) y2(t)
Dy1=diff(y1);
Dy2=diff(y2);
D2y1=diff(y1, 2);
D2y2=diff(y2, 2);
Eqn1=m*D2y1+2*k*y1-k*y2;
Eqn2=m*D2y2-k*y1+2*k*y2;
ICs=[y1(0)==0,Dy1(0)==0,Dy2(0)==0,y2(0)==0.01];
f=dsolve(Eqn1,Eqn2, ICs);
figure
ezplot(f.y1,[0 100]), hold on
ezplot(f.y2, [0, 100]), legend('y_1(t)', 'y_2(t)', 'location', 'best')
##### 3 CommentiMostra 1 commento meno recenteNascondi 1 commento meno recente
Sulaymon Eshkabilov il 18 Mag 2020
There two different ways of expressing ODE expressions. This is one of them and is the logically structured one. The other one is direct that you define your variable without specifying to differentuiate it w.r.t what variable that may create a problem in cases when there is an obscurity with the existing variables in your MATLAB workspace.
Good luck
Seungwon Lee il 18 Mag 2020
Thanks

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