Primitive of Cosine Function/Corollary

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Corollary to Primitive of Cosine Function

$\ds \int \cos a x \rd x = \frac {\sin a x} a + C$

where $a$ is a non-zero constant.


Proof

\(\ds \int \cos x \rd x\) \(=\) \(\ds \sin x + C\) Primitive of $\cos x$
\(\ds \leadsto \ \ \) \(\ds \int \cos a x \rd x\) \(=\) \(\ds \frac 1 a \paren {\sin a x} + C\) Primitive of Function of Constant Multiple
\(\ds \) \(=\) \(\ds \frac {\sin a x} a + C\) simplifying

$\blacksquare$


Also see


Sources