Primitive of Function of Natural Logarithm

Theorem

$\ds \int \map F {\ln x} \rd x = \int \map F u e^u \rd u$

where $u = \ln x$.


Proof

\(\ds u\) \(=\) \(\ds \ln x\)
\(\ds \leadsto \ \ \) \(\ds \frac {\d u} {\d x}\) \(=\) \(\ds \frac 1 x\) Derivative of Natural Logarithm Function
\(\ds \leadsto \ \ \) \(\ds \int \map F {\ln x} \rd x\) \(=\) \(\ds \int \map F u x \rd u\) Primitive of Composite Function
\(\ds \) \(=\) \(\ds \int \map F u e^u \rd u\) Definition of Exponential Function

$\blacksquare$


Sources

  • 1968: Murray R. Spiegel: Mathematical Handbook of Formulas and Tables ... (previous) ... (next): $\S 14$: Important Transformations: $14.56$
  • 2009: Murray R. Spiegel, Seymour Lipschutz and John Liu: Mathematical Handbook of Formulas and Tables (3rd ed.) ... (previous) ... (next): $\S 16$: Indefinite Integrals: Important Transformations: $16.56.$