If $y = {\cos ^2}\frac{{3x}}{2} - {\sin ^2}\frac{{3x}}{2}$, then $\frac{{{d^2}y}}{{d{x^2}}}$

JEE MATHEMATICS MCQ: DIFFERENTIATION

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Application +4 | -1

y = {\cos ^2}\frac{{3x}}{2} - {\sin ^2}\frac{{3x}}{2}

, then

\frac{{{d^2}y}}{{d{x^2}}}

View answer and explanation

Correct option: C

- 9y

Option C (-9y) is correct because the second derivative of y = cos(3x) is -9cos(3x), which is -9y.

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