How to plot a 2nd derivative equation

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Guan-Lin Chen 2020-11-20

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Hi all,

for equation like this

How to plot the graph with x(t) in y axis and t in x axis?

the code I use is this

syms  equ(t) x(t)
Dx = diff(x(t))
D2x = diff(x(t),2)
w = 1
% dt = 1/1000;
% t = 0:dt:1000*dt;                                     % Not needed Here
equ = D2x + (Dx)^3 + x(t)^2 *Dx + x(t) ;
%equ(t) = subs(equ, x, {exp(-1i*w*t)+exp(1i*w*t)})       % Substitute Expression For 
figure
fimplicit(equ, [-1 1])                                  % Use ‘fimplicit’ To Plot ‘equ(t)=0’
grid