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draw othorgonal trajectories using differential equations

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Brenda Galabe
Brenda Galabe 2018-12-12
评论： madhan ravi 2018-12-13
to draw orthogonal trajectories am i suppose to use dfield or is ezplot as shown below on the right track
Using the Matlab draw the families of orthogonal trajectories for the following differential equation 1) dy /dx = a*x*y /(b*x^2−c*y^2 )
2) dy/ dx = −d*x /e*y
syms y(x) x y
ode = diff(y,x) == (a*x*y)/(b*x^2-c*y^2);
ysol(x) = dsolve(ode)
ezplot(y(x))
error coming up

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采纳的回答

madhan ravi
madhan ravi 2018-12-12
Not more than two variables have to be symbolic so a,b,c valyes are assigned:
syms y(x)
a=2;
b=3;
c=5;
ode = diff(y,x) == (a*x*y)/(b*x^2-c*y^2);
ysol = vpa(dsolve(ode));
ezplot(ysol(1))
hold on
ezplot(ysol(2))
ezplot(ysol(3))
  1 个评论
Brenda Galabe
Brenda Galabe 2018-12-12
for second diff equation
syms y(x)
a=2;
b=3;
c=5;
d= 5;
e = 8;
ode = diff(y,x) == (-d*x)/(e*y);
ysol = vpa(dsolve(ode));
ezplot(ysol(1))
hold on
ezplot(ysol(2))
ezplot(ysol(3))
getting this error
index exceeds matrix dimensions.
Error in sym/subsref (line 776)
R_tilde = builtin('subsref',L_tilde,Idx);

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更多回答（1 个）

Brenda Galabe
Brenda Galabe 2018-12-12
thats for the first one correct ? do the same for the second. it worked great thanks
also when i get this error what does it mean
Warning: Explicit solution could not be found;
implicit solution returned.
> In dsolve (line 208)
  5 个评论
显示 3更早的评论
Brenda Galabe
Brenda Galabe 2018-12-13
编辑：madhan ravi 2018-12-13
FOR THE SECOND EQUATION KEEP GETTING AN EMPTY PLOT
ode = diff(y,x) == (-d*x)/(e*y);
ysol = vpa(dsolve(ode))
ysol =subs(ysol,'C2',25)
fplot(ysol(1))
hold on
fplot(ysol(2))
madhan ravi
madhan ravi 2018-12-13
syms y(x) C5 %C5 arises in ysol change it to your constant whether C2 or etc.. doesn't matter
d= 5;
e = 8;
dydx=diff(y);
ode = dydx == (-d*x)/(e*y);
ysol = vpa(dsolve(ode));
y1=subs(ysol,C5,4);
fplot({y1(1),y1(2)})
Screen Shot 2018-12-13 at 8.34.46 AM.png

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