Solving the Ordinary Differential Equation

2018 11 15
1 个回答
回答已采纳
更新时间：2018 11 15
12 次查看（30 天）

0 个投票

I am not sure how to solve these systems of differential equation. However, the final graph representation of the result is two exponential curves for and in respect to time.
Also, with =, the variable ks and BP are all constant.

请先登录，再回答此问题。

 采纳的回答

madhan ravi
madhan ravi 2018-11-15
编辑：madhan ravi 2018-11-15

0 个投票

EDITED
use dsolve()
or
Alternate method using ode45:
Screen Shot 2018-11-15 at 11.17.17 AM.png
tspan=[0 1];
y0=[0;0];
[t,x]=ode45(@myod,tspan,y0)
plot(t,x)
lgd=legend('Cp(t)','Cr(t)')
lgd.FontSize=20
function dxdt=myod(t,x)
tau=2;
ks=3;
BP=6;
k1=5;
k2=7;
x(1)=exp(-t)/tau; %x(1)->Cp
dxdt=zeros(2,1);
dxdt(1)=k1*x(1)-(k2/(1+BP))*x(2); %x(2)->Cr
dxdt(2)=k1*x(1)-k2*x(2);
end

9 个评论
显示 7更早的评论 隐藏 7更早的评论

Yeahh
Yeahh 2018-11-15
So should I set these two equations as two functions and then set some values to the variables? And ended with dsolve()?
madhan ravi
madhan ravi 2018-11-15
编辑：madhan ravi 2018-11-15
yes declare them by using syms Ct(t) Cr(t)
and then solve them
and use fplot(Ct(t)) to plot the curve
Yeahh
Yeahh 2018-11-15
What should I do with the constant variables?
madhan ravi
madhan ravi 2018-11-15
Substitute some numbers there
Yeahh
Yeahh 2018-11-15
I got something like this, but when I have the t defined, it is not running and I also need to know how to display the results as a plot
syms C_T(t) C_r(t);
t=[1:10000];
equations=[diff(C_T,t)==(3*exp(-t)-(3/(1+2))*C_T), diff(C_r,t)==(3*exp(-t)-3*C_r)];
sol=dsolve(equations);
Yeahh
Yeahh 2018-11-15
编辑：madhan ravi 2018-11-15
But the first differential equation is dcT/dt not Cp(t), is that the same?
madhan ravi's reply : no they are not the same
madhan ravi
madhan ravi 2018-11-15
dcT/dt refers to dxdt(1)
Yeahh
Yeahh 2018-11-15
编辑：madhan ravi 2018-11-15
Thank you so much, I have one last question.
What doest this line means?
dxdt=zeros(2,1);
madhan ravi
madhan ravi 2018-11-15
编辑：madhan ravi 2018-11-15
Anytime :), It is called preallocation(please google it) imagine as a container to store something. Make sure to accept for the answer if it was helpful.

请先登录，再进行评论。

更多回答（0 个）

类别

在 帮助中心 和 File Exchange 中查找有关 Common Operations 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by