Internal
problem
ID
[10041] Book
:
Own
collection
of
miscellaneous
problems Section
:
section
1.0 Problem
number
:
55 Date
solved
:
Monday, December 08, 2025 at 07:11:22 PM CAS
classification
:
[[_2nd_order, _quadrature]]
Hence this is the case of a double root \(\lambda _{1,2} = 0\). Therefore the solution is
\[ y= c_1 1 + c_2 t \tag {1} \]
Therefore the homogeneous
solution \(y_h\) is
\[
y_h = c_2 t +c_1
\]
The particular solution is now found using the method of undetermined
coefficients. Looking at the RHS of the ode, which is
\[ 1 \]
Shows that the corresponding
undetermined set of the basis functions (UC_set) for the trial solution is
\[ [\{1\}] \]
While the set of the
basis functions for the homogeneous solution found earlier is
\[ \{1, t\} \]
Since \(1\) is duplicated
in the UC_set, then this basis is multiplied by extra \(t\). The UC_set becomes
\[ [\{t\}] \]
Since
\(t\) is duplicated in the UC_set, then this basis is multiplied by extra \(t\). The UC_set
becomes
\[ [\{t^{2}\}] \]
Since there was duplication between the basis functions in the UC_set and the
basis functions of the homogeneous solution, the trial solution is a linear combination
of all the basis function in the above updated UC_set.
\[
y_p = A_{1} t^{2}
\]
The unknowns \(\{A_{1}\}\) are found
by substituting the above trial solution \(y_p\) into the ODE and comparing coefficients.
Substituting the trial solution into the ODE and simplifying gives
\[
2 A_{1} = 1
\]
Solving for the
unknowns by comparing coefficients results in
\[ \left [A_{1} = {\frac {1}{2}}\right ] \]
Substituting the above back in the
above trial solution \(y_p\), gives the particular solution
\[
y_p = \frac {t^{2}}{2}
\]
Therefore the general solution is
\begin{align*}
y &= y_h + y_p \\
&= \left (c_2 t +c_1\right ) + \left (\frac {t^{2}}{2}\right ) \\
\end{align*}
Summary of solutions found
\begin{align*}
y &= \frac {1}{2} t^{2}+c_2 t +c_1 \\
\end{align*}
Entering second order integrable as is solverIntegrating both sides of the ODE w.r.t \(t\) gives
\begin{align*} \int y^{\prime \prime }d t &= \int 1d t\\ y^{\prime } = t + c_1 \end{align*}
Which is now solved for \(y\). Entering first order ode quadrature solverSince the ode has the form \(y^{\prime }=f(t)\),
then we only need to integrate \(f(t)\).
\begin{align*} \int {dy} &= \int {t +c_1\, dt}\\ y &= \frac {1}{2} t^{2}+c_1 t + c_2 \end{align*}
Summary of solutions found
\begin{align*}
y &= \frac {1}{2} t^{2}+c_1 t +c_2 \\
\end{align*}
\begin{align*} y^{\prime \prime } &= 0 \tag {1} \\ A y^{\prime \prime } + B y^{\prime } + C y &= 0 \tag {2} \end{align*}
Comparing (1) and (2) shows that
\begin{align*} A &= 1 \\ B &= 0\tag {3} \\ C &= 0 \end{align*}
Applying the Liouville transformation on the dependent variable gives
\begin{align*} z(t) &= y e^{\int \frac {B}{2 A} \,dt} \end{align*}
Then (2) becomes
\begin{align*} z''(t) = r z(t)\tag {4} \end{align*}
Where \(r\) is given by
\begin{align*} r &= \frac {s}{t}\tag {5} \\ &= \frac {2 A B' - 2 B A' + B^2 - 4 A C}{4 A^2} \end{align*}
Substituting the values of \(A,B,C\) from (3) in the above and simplifying gives
\begin{align*} r &= \frac {0}{1}\tag {6} \end{align*}
Comparing the above to (5) shows that
\begin{align*} s &= 0\\ t &= 1 \end{align*}
Therefore eq. (4) becomes
\begin{align*} z''(t) &= 0 \tag {7} \end{align*}
Equation (7) is now solved. After finding \(z(t)\) then \(y\) is found using the inverse transformation
\begin{align*} y &= z \left (t \right ) e^{-\int \frac {B}{2 A} \,dt} \end{align*}
The first step is to determine the case of Kovacic algorithm this ode belongs to. There are 3 cases
depending on the order of poles of \(r\) and the order of \(r\) at \(\infty \). The following table summarizes these
cases.
Need to have at least one pole
that is either order \(2\) or odd order
greater than \(2\). Any other pole order
is allowed as long as the above
condition is satisfied. Hence the
following set of pole orders are all
allowed. \(\{1,2\}\),\(\{1,3\}\),\(\{2\}\),\(\{3\}\),\(\{3,4\}\),\(\{1,2,5\}\).
no condition
3
\(\left \{ 1,2\right \} \)
\(\left \{ 2,3,4,5,6,7,\cdots \right \} \)
Table 2.21: Necessary conditions for each Kovacic case
The order of \(r\) at \(\infty \) is the degree of \(t\) minus the degree of \(s\). Therefore
There are no poles in \(r\). Therefore the set of poles \(\Gamma \) is empty. Since there is no odd order pole
larger than \(2\) and the order at \(\infty \) is \(infinity\) then the necessary conditions for case one are met. Therefore
\begin{align*} L &= [1] \end{align*}
Since \(r = 0\) is not a function of \(t\), then there is no need run Kovacic algorithm to obtain a
solution for transformed ode \(z''=r z\) as one solution is
\[ z_1(t) = 1 \]
Using the above, the solution for the
original ode can now be found. The first solution to the original ode in \(y\) is found from
This is second order nonhomogeneous ODE. Let the solution be
\[
y = y_h + y_p
\]
Where \(y_h\) is the solution to the
homogeneous ODE
\[
A y''(t) + B y'(t) + C y(t) = 0
\]
And \(y_p\) is a particular solution to the nonhomogeneous ODE
\[
A y''(t) + B y'(t) + C y(t) = f(t)
\]
\(y_h\) is the
solution to
\[
y^{\prime \prime } = 0
\]
The homogeneous solution is found using the Kovacic algorithm which
results in
\[
y_h = c_2 t +c_1
\]
The particular solution is now found using the method of undetermined
coefficients. Looking at the RHS of the ode, which is
\[ 1 \]
Shows that the corresponding
undetermined set of the basis functions (UC_set) for the trial solution is
\[ [\{1\}] \]
While the set of the
basis functions for the homogeneous solution found earlier is
\[ \{1, t\} \]
Since \(1\) is duplicated
in the UC_set, then this basis is multiplied by extra \(t\). The UC_set becomes
\[ [\{t\}] \]
Since
\(t\) is duplicated in the UC_set, then this basis is multiplied by extra \(t\). The UC_set
becomes
\[ [\{t^{2}\}] \]
Since there was duplication between the basis functions in the UC_set and the
basis functions of the homogeneous solution, the trial solution is a linear combination
of all the basis function in the above updated UC_set.
\[
y_p = A_{1} t^{2}
\]
The unknowns \(\{A_{1}\}\) are found
by substituting the above trial solution \(y_p\) into the ODE and comparing coefficients.
Substituting the trial solution into the ODE and simplifying gives
\[
2 A_{1} = 1
\]
Solving for the
unknowns by comparing coefficients results in
\[ \left [A_{1} = {\frac {1}{2}}\right ] \]
Substituting the above back in the
above trial solution \(y_p\), gives the particular solution
\[
y_p = \frac {t^{2}}{2}
\]
Therefore the general solution is
\begin{align*}
y &= y_h + y_p \\
&= \left (c_2 t +c_1\right ) + \left (\frac {t^{2}}{2}\right ) \\
\end{align*}
Summary of solutions found
\begin{align*}
y &= \frac {1}{2} t^{2}+c_2 t +c_1 \\
\end{align*}
Which is now
solved for \(y \left (\tau \right )\). Entering second order ode missing \(y\) solverThis is second order ode with missing
dependent variable \(y \left (\tau \right )\). Let
For solution \(u \left (\tau \right ) = \frac {-\ln \left (\tau +\sqrt {\tau ^{2}-1}\right )+c_1}{\sqrt {\tau ^{2}-1}}\), since \(u=\frac {d}{d \tau }y \left (\tau \right )\) then we now have a new first order ode to solve which is
Entering first order ode quadrature solverSince the ode has the form \(\frac {d}{d \tau }y \left (\tau \right )=f(\tau )\), then we only need to
integrate \(f(\tau )\).