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If y = cos x.cos 2x.cos 3x then find its nth order derivative
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written 3.0 years ago by
teamques10
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We have
$y=\cos x \cdot \cos 2x \cdot \cos 3x$
$\therefore y = \dfrac {1}{2} \cdot \cos x \cdot 2\cos 2x \cdot \cos 3x = \dfrac {1}{2} \cdot \cos x \cdot \big [ \cos 5x + \cos x \big ]$
$\therefore y = \dfrac {1}{2} \cdot \cos x \cdot \cos …
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