- #1
squelch
Gold Member
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Homework Statement
Suppose that the characteristic equation to a second order, linear, homogeneous differential equation with constant coefficients yielded two complex roots:
[tex]\begin{array}{l}
{\lambda _1} = a + bi\\
{\lambda _2} = a - bi
\end{array}[/tex]
This would yield a general solution of:
[tex]y = {C_1}{e^{(a + bi)x}} + {C_2}{e^{(a - bi)x}}[/tex]
I would like to prove that this is equal to the expression:
[tex]y = {C_1}{e^{ax}}\sin (bx) + {C_2}{e^{ax}}\cos (bx)[/tex]
Homework Equations
Euler's identity:
[tex]{e^{ix}} = \cos (x) + i\sin (x)[/tex]
The Attempt at a Solution
At the end of the proof, I am left with the expression:
[tex]y = i{C_1}{e^{ax}}\sin (bx) + {C_2}{e^{ax}}\cos (bx)[/tex]
Can ##i## be "rolled up" into the constant of integration ##C_1## and the whole thing just defined as a single, undetermined constant?