# Example 1 de:=diff(x1(t),t)=-x1(t),diff(x2(t),t)=x1(t)-2*x2(t); dsolve({de},{x1(t),x2(t)}); # Example 3 de:=diff(x1(t),t)=-x1(t)-9*x2(t),diff(x2(t),t)=x1(t)-x2(t); ic:=x1(0)=300,x2(0)=0; dsolve({de,ic},{x1(t),x2(t)}); # Example 4 de:=diff(x1(t),t)=-x1(t)-9*x2(t),diff(x2(t),t)=x1(t)-x2(t); window:=x1=-400..400,x2=-100..100; tval:=-10..10: with(DEtools): DEplot({de},{x1(t),x2(t)},tval,window); de:=diff(x1(t),t)=-x1(t)-9*x2(t),diff(x2(t),t)=x1(t)-x2(t); dot:=(a,b)->[x1(0)=a,x2(0)=b]; ic:=[dot(300,0),dot(200,0),dot(100,50),dot(50,20)]; window:=x1=-400..400,x2=-100..100; tval:=-10..10: opts:=stepsize=0.05; with(DEtools): DEplot({de},{x1(t),x2(t)},tval,window,ic,opts); DEplot({de},{x1(t),x2(t)},t=0..8, [[x1(0)=300,x2(0)=0]],scene=[t,x1],stepsize=0.05);