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Home  >>  JEEMAIN and AIPMT  >>  Mathematics  >>  Class12  >>  Integral Calculus
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Integrate : $\cos ^3 x dx$

$(a)\;\frac{-3}{4} \sin x +\frac{1}{12} \sin 3x +c \\(b)\;\frac{3}{4} \sin x +\frac{1}{12} \sin 3x +c \\(c)\;\frac{3}{4} \cos +\frac{1}{12} \cos 3x+c \\ (d)\;None$

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1 Answer

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Use trigonometry property:-
$\cos^3 x= \large\frac{3 \cos x + \cos 3x}{4}$
=> $\large\frac{1}{4}$$\int 3 \cos x +\cos 3x dx$
$\large\frac{3}{4} $$\sin x +\large\frac{1}{12}$$ \sin 3x +c$
Hence b is the correct answer.
answered Jan 3, 2014 by meena.p
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