MCQ
જો $y = A\cos nx + B\sin nx,$ તો ${{{d^2}y} \over {d{x^2}}} = $
- A${n^2}y$
- B$ - y$
- ✓$ - {n^2}y$
- Dએકપણ નહીં
$\therefore dy/dx = - nA\sin (nx) + nB\cos (nx)$
Again $\frac{{{d^2}y}}{{d{x^2}}} = - {n^2}A\cos (nx) - {n^2}B\sin (nx)$
$ = - {n^2}[A\cos (nx) + B\sin (nx)]$
==> $\frac{{{d^2}y}}{{d{x^2}}} = - {n^2}y$.
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