Student[ODEs][ReduceOrder]
LinearParticularSolution
Reduce the order of a linear ODE using a particular solution
Calling Sequence
Parameters
Description
Examples
Compatibility
LinearParticularSolution(ODE, y(x) = psol)
LinearParticularSolution(ODE, y(x) = psol, u(t))
ODE
-
second order linear ordinary differential equation
y(x) = psol
equation; a particular solution of the ODE
y
name; the original dependent variable
x
name; the original independent variable
u
name; the dependent variable for the reduced ODE
t
name; the independent variable for the reduced ODE
The LinearParticularSolution(ODE, psol) command reduces the order of a second order linear ODE using a particular solution.
The second argument must be a particular solution of the ODE of the form y(x) = psol, where psol does not depend on y(x).
The third argument, u(t), representing the variable for the reduced ODE, is optional. If it is not given, new independent and dependent variables will be chosen which do not conflict with the existing variables.
The default output is a sequence consisting of the reduced ODE in terms of the new variables, followed by the transformation used to recover the original ODE from the reduced ODE.
If an extra option solve or solve=true is also given, an attempt is made to solve the reduced ODE and return the general solution to the original ODE. If successful, the general solution of the original ODE will be returned.
If the option solve is given and furthermore, the extra option output=basis is given, then as above an attempt will be made to find the general solution to the original ODE, but the answer will be returned in the form of a list of particular solutions forming a basis for that general solution.
with⁡StudentODEs:
with⁡StudentODEsReduceOrder:
Given a linear homogeneous ODE:
ode≔x−1⁢diff⁡y⁡x,x,x−x⁢diff⁡y⁡x,x+y⁡x=0
ode≔x−1⁢ⅆ2ⅆx2y⁡x−x⁢ⅆⅆxy⁡x+y⁡x=0
And a particular solution for it:
psol≔y⁡x=exp⁡x
psol≔y⁡x=ⅇx
Use the particular solution to find a new ODE of reduced order which can be used to solve the original:
reduced_ode,tr≔LinearParticularSolution⁡ode,psol
reduced_ode,tr≔ⅆⅆtu⁡t=−u⁡t⁢t−2t−1,t=x,u⁡t=ⅆⅆxy⁡xⅇx
Solve the reduced order ODE:
reduced_sol≔Solve⁡reduced_ode,u⁡t
reduced_sol≔u⁡t=ⅇ−t+_C1⁢t−1
Apply the transformation to find a simpler ODE for the original variable y(x):
new_ode≔eval⁡reduced_sol,tr
new_ode≔ⅆⅆxy⁡xⅇx−y⁡xⅇx=ⅇ−x+_C1⁢x−1
Solve the simpler ODE to find the general solution of the original ODE:
gensol1≔Solve⁡new_ode,y⁡x
gensol1≔y⁡x=−ⅇx⁢x⁢ⅇ−x+_C1−_C2
Alternatively, the particular solution can be used to solve the original ODE in a single step if we use the option solve:
gensol≔LinearParticularSolution⁡ode,psol,solve
gensol≔y⁡x=ⅇx⁢−x⁢ⅇ−x+_C1+_C2
Simplify the form of the general solution:
simplify⁡expand⁡gensol
y⁡x=−x⁢ⅇ_C1+ⅇx⁢_C2
Use the output=basis option instead:
Basis≔LinearParticularSolution⁡ode,psol,solve,output=basis
Basis≔x,ⅇx
Show the new solution:
sol≔y⁡x=remove⁡`=`,Basis,rhs⁡psol1
sol≔y⁡x=x
Calculate the Wronskian of the two solutions for y(x):
W≔VectorCalculus:-Wronskian⁡Basis,x
W≔xⅇx1ⅇx
The determinant should be nonzero to prove independence of the solutions:
simplify⁡LinearAlgebra:-Determinant⁡W
ⅇx⁢x−1
The Student[ODEs][ReduceOrder][LinearParticularSolution] command was introduced in Maple 2021.
For more information on Maple 2021 changes, see Updates in Maple 2021.
See Also
dsolve
Student
Student[ODEs]
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