Primitive of Reciprocal of q plus p by Hyperbolic Secant of a x
Jump to navigation
Jump to search
Theorem
- $\ds \int \frac {\d x} {q + p \sech a x} = \frac x q - \frac p q \int \frac {\d x} {p + q \cosh a x} + C$
Proof
\(\ds \int \frac {\d x} {q + p \sech a x}\) | \(=\) | \(\ds \frac 1 q \int \frac {q \rd x} {q + p \sech a x}\) | multiplying top and bottom by $q$ | |||||||||||
\(\ds \) | \(=\) | \(\ds \frac 1 q \int \frac {\paren {q + p \sech a x - p \sech a x} \rd x} {q + p \sech a x}\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds \frac 1 q \int \frac {\paren {q + p \sech a x} \rd x} {q + p \sech a x} - \frac p q \int \frac {\sech a x \rd x} {q + p \sech a x}\) | Linear Combination of Primitives | |||||||||||
\(\ds \) | \(=\) | \(\ds \frac 1 q \int \d x - \frac p q \int \frac {\sech a x \rd x} {q + p \sech a x}\) | simplifying | |||||||||||
\(\ds \) | \(=\) | \(\ds \frac x q - \frac p q \int \frac {\sech a x \rd x} {q + p \sech a x} + C\) | Primitive of Constant | |||||||||||
\(\ds \) | \(=\) | \(\ds \frac x q - \frac p q \int \frac {\d x} {\frac q {\sech a x} + p} + C\) | multiplying top and bottom by $\dfrac 1 {\sech a x}$ | |||||||||||
\(\ds \) | \(=\) | \(\ds \frac x q - \frac p q \int \frac {\d x} {p + q \cosh a x} + C\) | Definition 2 of Hyperbolic Secant |
$\blacksquare$
Also see
Sources
- 1968: Murray R. Spiegel: Mathematical Handbook of Formulas and Tables ... (previous) ... (next): $\S 14$: Integrals involving $\sech a x$: $14.634$