Primitive of Inverse Hyperbolic Cosine of x over a over x squared/Corollary
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Theorem
- $\ds \int \frac 1 {x^2} \paren {-\cosh^{-1} \dfrac x a} \rd x = -\frac 1 x \paren {-\cosh^{-1} \dfrac x a} - \frac 1 a \arcsec \size {\frac x a} + C$
where $-\cosh^{-1}$ denotes the negative branch of the real inverse hyperbolic cosine multifunction.
Proof
\(\ds -\cosh^{-1} \frac x a\) | \(=\) | \(\ds -\arcosh \frac x a\) | Definition of Real Inverse Hyperbolic Cosine | |||||||||||
\(\ds \leadsto \ \ \) | \(\ds \int \frac 1 {x^2} \paren {-\cosh^{-1} \dfrac x a} \rd x\) | \(=\) | \(\ds -\int \frac 1 {x^2} \arcosh \dfrac x a \rd x\) | |||||||||||
\(\ds \) | \(=\) | \(\ds -\paren {-\frac 1 x \arcosh \dfrac x a + \frac 1 a \arcsec \size {\frac x a} + C}\) | Primitive of $\frac 1 {x^2} \arcosh \dfrac x a$ | |||||||||||
\(\ds \) | \(=\) | \(\ds -\frac 1 x \paren {-\cosh^{-1} \dfrac x a} - \frac 1 a \arcsec \size {\frac x a} + C\) | Definition of Real Inverse Hyperbolic Cosine |
$\blacksquare$
Sources
- 1968: Murray R. Spiegel: Mathematical Handbook of Formulas and Tables ... (previous) ... (next): $\S 14$: Integrals involving Inverse Hyperbolic Functions: $14.655$