Primitive of Hyperbolic Sine of a x by Hyperbolic Cosine of a x/Proof 5

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Theorem

$\ds \int \sinh a x \cosh a x \rd x = \frac {\sinh^2 a x} {2 a} + C$


Proof

\(\ds u\) \(=\) \(\ds \sinh a x\)
\(\ds \leadsto \ \ \) \(\ds \frac {\d u} {\d x}\) \(=\) \(\ds a \cosh a x\) Derivative of $\sinh a x$
\(\ds \leadsto \ \ \) \(\ds \int \sinh a x \cosh a x \rd x\) \(=\) \(\ds \int \frac u a \rd u\) Integration by Substitution
\(\ds \) \(=\) \(\ds \frac 1 a \int u \rd u\) Primitive of Constant Multiple of Function
\(\ds \) \(=\) \(\ds \frac 1 a \frac {u^2} 2 + C\) Primitive of Power
\(\ds \) \(=\) \(\ds \frac {\sinh^2 a x} {2 a} + C\) substituting for $u$

$\blacksquare$