| > | with(LinearAlgebra):with(plots):with(DEtools): |
Warning, the name changecoords has been redefined
Separation/Inhomogeneous
| > | A:=Matrix([[3,-1],[-2,4]]); |
| > | de1:=diff(x1(t),t)=3*x1(t)-x2(t)+6; |
| > | de2:=diff(x2(t),t)=-2*x1(t)+4*x2(t)+12; |
| > | dsolve({de1,de2}); |
| > | dfieldplot([de1,de2],[x1(t),x2(t)],t=0..1,x1=-8..2,x2=-8..2,arrows=MEDIUM); |
| > |
![[Plot]](images/lecture8_5.gif)
Inhomogeneous, nonautonomous
| > | A:=Matrix([[1,1],[4,1]]); |
| > | E:=Eigenvectors(A); |
| > | M:=Matrix([[-1,1],[2,2]]); |
| > | C:=Matrix([[-1,0],[0,3]]); |
| > | M.C.M^(-1); |
| > | g1(t):=exp(2*t);g2(t):=sin(t); |
| > | de1:=diff(x1(t),t)=x1(t)+x2(t)+g1(t); |
| > | de2:=diff(x2(t),t)=4*x1(t)+x2(t)+g2(t); |
| > | gv:=Matrix([[g1(t)],[g2(t)]]); |
| > | h:=M^(-1).gv; |
| > | h[1,1]; |
| > | den1:=diff(y1(t),t)=-y1(t)+h[1,1]; |
| > | den2:=diff(y2(t),t)=3*y2(t)+h[2,1]; |
| > | sol:=dsolve({den1,den2}); |
| > | y1s:=solve(sol[2],y1(t)); |
| > | y2s:=solve(sol[1],y2(t)); |
| > | xsol:=M.Matrix([[y1s],[y2s]]); |
| > | r:=A.xsol+gv; |
| > | expand(r[1,1]); |
| > | expand(diff(xsol[1,1],t)); |
| > | expand(r[2,1]); |
| > | expand(diff(xsol[2,1],t)); |
| > |
Higher Dimensional Eigenspaces
| > | A:=Matrix([[3,-18,-4,39,20],[0,11,2,-20,-10],[0,9,4,-20,-10],[0,-18,-4,42,20],[0,45,10,-100,-48]]); |
| > | c:=CharacteristicPolynomial(A,x); |
| > | solve(c,x); |
| > | M:=Matrix([[0,1,0,1,0],[-2/9,20/9,10/9,0,1/5],[1,0,0,0,1/5],[0,1,0,0,-2/5],[0,0,1,0,1]]); |
| > | M^(-1).A.M; |
| > | gv:=Matrix([[cos(t)],[sin(t)],[exp(5*t)],[exp(2*t)],[t*exp(2*t)]]); |
| > | h:=M^(-1).gv; |
| > | de1:=diff(y1(t),t)=2*y1(t)+h[1,1]; |
| > | de2:=diff(y2(t),t)=2*y2(t)+h[2,1]; |
| > | de3:=diff(y3(t),t)=2*y1(t)+h[3,1]; |
| > | de4:=diff(y4(t),t)=3*y4(t)+h[4,1]; |
| > | de5:=diff(y5(t),t)=3*y1(t)+h[5,1]; |
| > | sol:=dsolve({de1,de2,de3,de4,de5}); |

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| > | yv:=Matrix([[solve(sol[1],y1(t))],[solve(sol[3],y2(t))],[solve(sol[5],y3(t))],[solve(sol[2],y4(t))],[solve(sol[4],y5(t))]]); |
| > | xsol:=M.yv; |
![xsol := Matrix([[-10*exp(2*t)*t^2-21/10*cos(t)-17/10*sin(t)-2/3*exp(5*t)-59*t*exp(2*t)+exp(2*t)*_C5-59*exp(2*t)+exp(3*t)*_C4], [1/5*_C1-293/25*sin(t)+107/90*exp(2*t)*_C3+10/9*_C2-293/18*exp(2*t)*t^2+5...](images/lecture8_47.gif)
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| > | r:=A.xsol+gv: |
| > | r[1,1]; |
| > | diff(xsol[1,1],t); |
| > |
| > |
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