- #1
tomeatworld
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Homework Statement
Find complex number [tex]\lambda[/tex] such that e[tex]\lambda[/tex]t solves
[tex]\frac{d^{2}y}{dt^{2}}[/tex] + 4[tex]\frac{dy}{dt}[/tex] + 5y = 0
Express this solution in the form eat(cos(bt) + i sin(bt))
Homework Equations
The Attempt at a Solution
So the first part is fine, using [tex]\lambda[/tex]2 + 4[tex]\lambda[/tex] + 5 = 0 to get values of [tex]\lambda[/tex] at -2[tex]\pm[/tex]i. From here, I've been taught to use:
y = Ae[tex]\lambda[/tex]1t + Be[tex]\lambda[/tex]2t but this time, it doesn't help get to the required form.
Using what I've mention, I can get to A=-2 but finding B seems to be a mystery. Any help greatly appreciated!