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anonymous
 4 years ago
Can someone help me to solve this differential eqation please.
y''+9y=cosx
(i got solution to homogeneuos equation: c1*cos(3x)+c2*sin(3x) )
i have tried to find particular with variation of parameters, with wronskian...i have so weird integral :(
anonymous
 4 years ago
Can someone help me to solve this differential eqation please. y''+9y=cosx (i got solution to homogeneuos equation: c1*cos(3x)+c2*sin(3x) ) i have tried to find particular with variation of parameters, with wronskian...i have so weird integral :(

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anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0try going to wolframalpha.com

lalaly
 4 years ago
Best ResponseYou've already chosen the best response.2have u tried undetermined coeffecients?

lalaly
 4 years ago
Best ResponseYou've already chosen the best response.2\[y_p=Acosx + Bsinx\]\[y_p'=Asinx+Bcosx\]\[y_p''=AcosxBsinx\]substitute in equation \[AcosxBsinx+9(Acosx+Bsinx)=cosx\]\[AcosxBsinx+9Acosx +9Bsinx=cosx\]\[8Acosx+8Bsinx=cosx\]\[8A=1\]\[A=\frac{1}{8}\]\[8B=0\]\[B=0\] so \[y_p=\frac{1}{8}cosx\]\[y=y_h + y_p\]\[=c_1\cos3x+c_2\sin3x +\frac{1}{8}cosx\]
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