Primitive of Square of Secant of a x

Theorem

$\ds \int \sec^2 a x \rd x = \frac {\tan a x} a + C$


Proof

\(\ds \int \sec^2 x \rd x\) \(=\) \(\ds \tan x + C\) Primitive of $\sec^2 x$
\(\ds \leadsto \ \ \) \(\ds \int \sec^2 a x \rd x\) \(=\) \(\ds \frac 1 a \paren {\tan a x} + C\) Primitive of Function of Constant Multiple
\(\ds \) \(=\) \(\ds \frac {\tan a x} a + C\) simplifying

$\blacksquare$


Also see


Sources

  • 1968: Murray R. Spiegel: Mathematical Handbook of Formulas and Tables ... (previous) ... (next): $\S 14$: Integrals involving $\sec a x$: $14.452$
  • 1968: George B. Thomas, Jr.: Calculus and Analytic Geometry (4th ed.) ... (previous) ... (next): Back endpapers: A Brief Table of Integrals: $90$.
  • 2009: Murray R. Spiegel, Seymour Lipschutz and John Liu: Mathematical Handbook of Formulas and Tables (3rd ed.) ... (previous) ... (next): $\S 17$: Tables of Special Indefinite Integrals: $(22)$ Integrals Involving $\sec a x$: $17.22.2.$