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posted by  rjboogey on 11/30/2008 9:24:30 PM  |  status: Closed  

Will rate highly..linear differential equaton

Course Textbook Chapter Problem
Calculus N/A N/A N/A
Question Details:
y'' + 9y = 0; \quad y = 3, \; y'=3 \;\textnormal{at}\; x = \pi/3
y(x) =
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posted by roydesoto on 11/30/2008 9:29:06 PM  |  status: Live
Asker's Rating: Lifesaver   
Response Details:
char. poly is r^2 + 9 = 0 so general soln is y = Acos(3x) + Bsin(3x)

y' = -3Asin(3x) + 3Bcos(3x)

plug in intitial values:

3 = Acos(π) + Bsin(π) = -A ==> A = -3

3 = -3Asin(π) + 3Bcos(π) = -3B ==> B = -1

so soln is: y = -3cos(3x) - sin(3x)
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posted by A-Rod 7821 on 11/30/2008 9:37:01 PM  |  status: Live
Asker's Rating: Helpful   
rjboogey's comment:
"I just finished and C2 is also neg..but i appreciate it"
Response Details:
First Initial Condition:
Second Initial Condition is when
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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