- #1
roam
- 1,271
- 12
Homework Statement
Find the general solution to the following differential equation:
[itex]\frac{d^2 y}{dt^2} - 2 \frac{dy}{dt} + 2y =e^t[/itex]
The correct answer must be: [itex]y(t) = C_1 e^t \cos t + C_2 e^2 \sin t +e^t[/itex]
The Attempt at a Solution
I haven't been able to get the correct answer so far. The eigenvalues are:
[itex]\lambda^2-2 \lambda +2 = 0[/itex]
[itex]\lambda = \frac{2 \pm \sqrt{4-8}}{2} = 1 \pm i[/itex]
So the general solution of the corresponding homogeneous equation is:
[itex]y_h(t) = C_1 e^{(1-i)t} + C_2 e^{(1-i)t} [/itex]
And with inspection a particular solution is yp = et, so the general solution must be:
[itex]y(t) = C_1 e^{(1-i)t} + C_2 e^{(1-i)t} + e^t[/itex]
Using Euler's formula:
[itex]y(t) = C_1 \frac{e^t}{\cos t + i \sin t} + C_2 e^t (\cos t + i \sin t)+ e^t[/itex]
So, why is my answer so different from the correct answer provided? What do I have to do in order to get the correct answer?
Any help is really appreciated.