Find the solution of the Euler equation on (0, ∞) with initial conditions x²y'' + xy' + y = 0, y(1) = 3, y’(1) = 1 y(x) =

Advanced Engineering Mathematics
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Author:Erwin Kreyszig
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Chapter2: Second-order Linear Odes
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### Solving the Euler Equation

Consider the following differential equation defined on the interval \( (0, \infty) \):

\[ x^2 y'' + x y' + y = 0 \]

where \( y(1) = 3 \) and \( y'(1) = 1 \).

To find the solution to this Euler equation, follow these steps:

1. **Substitute the general solution structure**: Assume \( y = x^r \). Substituting \( y = x^r \) into the differential equation gives:

   \[ x^2 (r(r-1)x^{r-2}) + x (r x^{r-1}) + x^r = 0 \]

2. **Simplify the terms**: This simplifies to:

   \[ r(r-1)x^r + r x^r + x^r = 0 \]

3. **Factor out the common term**: Factor out \( x^r \):

   \[ x^r (r^2 - r + r + 1) = 0 \]

   \[ x^r (r^2 + 1) = 0 \]

4. **Solve for \( r \)**: The characteristic equation is:

   \[ r^2 + 1 = 0 \]

   Solving for \( r \), we get:

   \[ r = \pm i \]

   Thus, the general solution is:

   \[ y(x) = c_1 \cos(\ln(x)) + c_2 \sin(\ln(x)) \]

5. **Apply the initial conditions**:
   
   - \( y(1) = 3 \):
     \[ y(1) = c_1 \cos(0) + c_2 \sin(0) = c_1 = 3 \]
   
   - \( y'(x) \):
     \[ y'(x) = c_1 \left( -\frac{\sin(\ln(x))}{x} \right) + c_2 \left( \frac{\cos(\ln(x))}{x} \right) \]
     
     \( y'(1) = 1 \):
     \[ 1 = c_1(-\sin(0)) + c_2(\cos(0)) = c_2 \Rightarrow c_2 =
Transcribed Image Text:### Solving the Euler Equation Consider the following differential equation defined on the interval \( (0, \infty) \): \[ x^2 y'' + x y' + y = 0 \] where \( y(1) = 3 \) and \( y'(1) = 1 \). To find the solution to this Euler equation, follow these steps: 1. **Substitute the general solution structure**: Assume \( y = x^r \). Substituting \( y = x^r \) into the differential equation gives: \[ x^2 (r(r-1)x^{r-2}) + x (r x^{r-1}) + x^r = 0 \] 2. **Simplify the terms**: This simplifies to: \[ r(r-1)x^r + r x^r + x^r = 0 \] 3. **Factor out the common term**: Factor out \( x^r \): \[ x^r (r^2 - r + r + 1) = 0 \] \[ x^r (r^2 + 1) = 0 \] 4. **Solve for \( r \)**: The characteristic equation is: \[ r^2 + 1 = 0 \] Solving for \( r \), we get: \[ r = \pm i \] Thus, the general solution is: \[ y(x) = c_1 \cos(\ln(x)) + c_2 \sin(\ln(x)) \] 5. **Apply the initial conditions**: - \( y(1) = 3 \): \[ y(1) = c_1 \cos(0) + c_2 \sin(0) = c_1 = 3 \] - \( y'(x) \): \[ y'(x) = c_1 \left( -\frac{\sin(\ln(x))}{x} \right) + c_2 \left( \frac{\cos(\ln(x))}{x} \right) \] \( y'(1) = 1 \): \[ 1 = c_1(-\sin(0)) + c_2(\cos(0)) = c_2 \Rightarrow c_2 =
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