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Particular integral of (D2 + 9)y = sin3x. |
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Answer» (D2 + 9)y = sin3x It's auxiliarly equation is m2 + 9 = 0 ⇒ m = \(\pm\) 3c \(\therefore\) C.F. = c1 cos3x + c2 sin3x P.I. = \(\frac1{D^2 + 9} sin3x\) \( = \frac{-x}{2\times3} cos3x\) \(\left(\because \frac1{D^2 + a^2}sin\,ax = \frac{-x\,cos \,ax}{2a}\right)\) \( = \frac{-x}{6}cos3x\) Particular integral = \( \frac{-x}{6}cos3x\) |
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