Try this way

serilas — Thu, 18 Mar 2010 12:58:41 Z

Try this way:

> restart: with(plots):
> n:=0.5:
> Eqn:= 6+(1+(1.444714922*(.288189107+.288745018- .806878862))*sin(1.726958075*t))*t/(.74231747+t/(20-6)):
>Eq:=6+(1+(3.5*(.288189107+.288745018-.806878862))*sin(1.726958075*t))*t/(.74231747+t/(20-6)):
>sol1:=dsolve({diff(Log10S(t),t)=-(.178131-0.6814e-1*Eqn+0.16242e-1*Eqn^1.5)*n*(-Log10S(t))^((n-1)/n), Log10S(0)= -0.1e-3}, numeric):
>sol2:=dsolve({diff(Log10S(t),t)=-(.178131-0.6814e-1*Eq+0.16242e-1*Eq^1.5)*n*(-Log10S(t))^((n-1)/n), Log10S(0)= -0.1e-3}, numeric):
> f1:=odeplot(sol1,[t,Log10S(t)],0..5, color=blue,linestyle=3, thickness=2):
f2:=odeplot(sol2,[t,Log10S(t)],0..5, color=green,linestyle=3, thickness=2):
> display(f1,f2);

MaplePrimes - answers and comments on Question, Plotting two or more ODE on one plot

Try this way