JAMB 2011 · UTME · Q40

Calculus (JAMB bridge)

Find $\displaystyle\int \cos 4x\,dx$ .

Worked solution (try it first)

$\cos$ integrates to $\sin$ .
For $\cos4x$ , also divide by 4, the coefficient of $x$ .
So $\int\cos4x\,dx = \frac14\sin4x + k$ , option D.
Check: $\frac{d}{dx}\left(\frac14\sin4x\right) = \cos4x$ .

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