Logarithm
The (single-valued) logarithm $\log \colon \mathbb{C} \setminus (-\infty,0] \rightarrow \mathbb{C}$ defined by the formula $$\log(z) = \displaystyle\int_1^z \dfrac{1}{t} \mathrm{d}t,$$ where we understand the integral $\displaystyle\int_1^z$ as a contour integral over a path from $1$ to $z$ that does not intersect the set $(-\infty,0] \subset \mathbb{C}$.
Graph of $\log$ on $(0,10]$.
Domain coloring of $\log$.
Properties
Logarithm of a complex number
Derivative of the logarithm
Real and imaginary parts of log
Relationship between logarithm (multivalued) and logarithm
Logarithm of product is a sum of logarithms
Logarithm of a quotient is a difference of logarithms
Relationship between logarithm and positive integer exponents
Logarithm of 1
Logarithm diverges to negative infinity at 0 from right
Logarithm at minus 1
Logarithm at i
Logarithm at -i
Taylor series of $\log(1-z)$
Taylor series of $\log(1+z)$
Antiderivative of the logarithm
Z2F1(1,1;2,-z) equals log(1+z)
Exponential integral Ei series
Relationship between prime zeta, Möbius function, logarithm, and Riemann zeta
The prime number theorem
Series for log(z) for Re(z) greater than 1/2
Series for log(z) for absolute value of (z-1) less than 1
Series for log(z) for Re(z) greater than 0
Laurent series for log((z+1)/(z-1)) for absolute value of z greater than 1
Series for log(z+a) for positive a and Re(z) greater than -a
Relationship between logarithm and Mangoldt
Log e(z)=log(z)
Log 10(z)=log(z)/log(10)
Log 10(z)=log 10(e)log(z)
Log(z)=log(10)log 10(z)
Limit of log(x)/x^a=0
Limit of x^a log(x)=0
X/(1+x) less than log(1+x)
Log(1+x) less than x
X less than -log(1-x)
-log(1-x) less than x/(1-x)
Abs(log(1-x)) less than 3x/2
Log(x) less than or equal to x-1
Log(x) less than or equal to n(x^(1/n)-1)
Abs(log(1+z)) less than or equal to -log(1-abs(z))
Log(1+z) as continued fraction
Log((1+z)/(1-z)) as continued fraction
References
- 1964: Milton Abramowitz and Irene A. Stegun: Handbook of mathematical functions ... (previous) ... (next): $4.1.1$
- 1964: Milton Abramowitz and Irene A. Stegun: Handbook of mathematical functions ... (previous) ... (next): $4.1.48$
