# List of limits

This is a list of limits for common functions. Note that a and b are constants with respect to x. Algebra of limits

## Limits for general functions

${\text{If }}\lim _{x\to c}f(x)=L_{1}{\text{ and }}\lim _{x\to c}g(x)=L_{2}{\text{ then:}}$ $\lim _{x\to c}\,[f(x)\pm g(x)]=L_{1}\pm L_{2}$ $\lim _{x\to c}\,[f(x)g(x)]=L_{1}\times L_{2}$ $\lim _{x\to c}{\frac {f(x)}{g(x)}}={\frac {L_{1}}{L_{2}}}\qquad {\text{ if }}L_{2}\neq 0$ $\lim _{x\to c}\,f(x)^{n}=L_{1}^{n}\qquad {\text{ if }}n{\text{ is a positive integer}}$ $\lim _{x\to c}\,f(x)^{1 \over n}=L_{1}^{1 \over n}\qquad {\text{ if }}n{\text{ is a positive integer, and if }}n{\text{ is even, then }}L_{1}>0$ $\lim _{x\to c}{\frac {f(x)}{g(x)}}=\lim _{x\to c}{\frac {f'(x)}{g'(x)}}\qquad {\text{ if }}\lim _{x\to c}f(x)=\lim _{x\to c}g(x)=0{\text{ or }}\pm \infty$ (L'Hôpital's rule)

## Limits of general functions

$\lim _{h\to 0}{f(x+h)-f(x) \over h}=f'(x)$ $\lim _{h\to 0}\left({\frac {f(x+h)}{f(x)}}\right)^{\frac {1}{h}}=\exp \left({\frac {f'(x)}{f(x)}}\right)$ $\lim _{h\to 0}{\left({f(x(1+h)) \over {f(x)}}\right)^{1 \over {h}}}=\exp \left({\frac {xf'(x)}{f(x)}}\right)$ ## Notable special limits

$\lim _{x\to 0}\left(1+x\right)^{\frac {1}{x}}=e$ $\lim _{n\to \infty }{\frac {n}{\sqrt[{n}]{n!}}}=e$ $\lim _{n\to \infty }\,2^{n}\underbrace {\sqrt {2-{\sqrt {2+{\sqrt {2+{\text{...}}+{\sqrt {2}}}}}}}} _{n}=\pi$ $\lim _{x\to +\infty }\left(1+{\frac {1}{x}}\right)^{x}=e$ $\lim _{x\to +\infty }\left(1-{\frac {1}{x}}\right)^{x}={\frac {1}{e}}$ $\lim _{x\to +\infty }\left(1+{\frac {k}{x}}\right)^{mx}=e^{mk}$ $\lim _{x\to +\infty }\left({\frac {x}{x+k}}\right)^{x}={\frac {1}{e^{k}}}$ $\lim _{x\to 0}\left({\frac {a^{x}-1}{x}}\right)=\ln {a},\qquad \forall ~a>0$ $\lim _{x\to 0}\left(1+a\left({e^{-x}-1}\right)\right)^{-{\frac {1}{x}}}=e^{a}\qquad {\text{Follows from }}$ ***

## Simple functions

$\lim _{x\to c}a=a$ $\lim _{x\to c}x=c$ $\lim _{x\to c}ax+b=ac+b$ $\lim _{x\to c}x^{r}=c^{r}\qquad {\mbox{ if }}r{\mbox{ is a positive integer}}$ $\lim _{x\to 0^{+}}{\frac {1}{x^{r}}}=+\infty$ $\lim _{x\to 0^{-}}{\frac {1}{x^{r}}}={\begin{cases}-\infty ,&{\text{if }}r{\text{ is odd}}\\+\infty ,&{\text{if }}r{\text{ is even}}\end{cases}}$ ## Logarithmic and exponential functions

$\lim _{x\to 0}xe^{-x}=0$ $\lim _{x\to \infty }xe^{-x}=0$ $\lim _{x\to 1}{\frac {\ln(x)}{x-1}}=1$ or

$\lim _{y\to 0}{\frac {\ln(y+1)}{y}}=1$ ${\mbox{For }}a>1:$ $\lim _{x\to 0^{+}}\log _{a}x=-\infty$ $\lim _{x\to \infty }\log _{a}x=\infty$ ${\mbox{For }}a<1:$ $\lim _{x\to 0^{+}}\log _{a}x=\infty$ $\lim _{x\to \infty }\log _{a}x=-\infty$ $\lim _{x\to 0}{\frac {-\ln \left(1+a\left({e^{-x}-1}\right)\right)}{x}}=a\quad {\text{*** Follows from}}$ L'Hôpital's rule

## Trigonometric functions

$\lim _{x\to a}\sin x=\sin a$ $\lim _{x\to a}\cos x=\cos a$ If $x$ is expressed in radians:

$\lim _{x\to 0}{\frac {\sin x}{x}}=1$ $\lim _{x\to 0}{\frac {\sin ax}{ax}}=1\qquad {\mbox{ for }}a\neq 0$ $\lim _{x\to 0}{\frac {1-\cos x}{x}}=0$ $\lim _{x\to 0}{\frac {1-\cos x}{x^{2}}}={\frac {1}{2}}$ $\lim _{x\to n^{\pm }}\tan \left(\pi x+{\frac {\pi }{2}}\right)=\mp \infty \qquad {\text{for any integer }}n$ $\lim _{x\to 0}{\frac {\sin ax}{x}}=a$ $\lim _{x\to 0}{\frac {\sin ax}{bx}}={\frac {a}{b}}\qquad {\mbox{ for }}b\neq 0$ ## Near infinities

$\lim _{x\to \infty }N/x=0{\text{ for any real }}N$ $\lim _{x\to \infty }x/N={\begin{cases}\infty ,&N>0\\{\text{does not exist}},&N=0\\-\infty ,&N<0\end{cases}}$ $\lim _{x\to \infty }x^{N}={\begin{cases}\infty ,&N>0\\1,&N=0\\0,&N<0\end{cases}}$ $\lim _{x\to \infty }N^{x}={\begin{cases}\infty ,&N>1\\1,&N=1\\0,&0 $\lim _{x\to \infty }N^{-x}=\lim _{x\to \infty }1/N^{x}=0{\text{ for any }}N>1$ $\lim _{x\to \infty }{\sqrt[{x}]{N}}={\begin{cases}1,&N>0\\0,&N=0\\{\text{does not exist}},&N<0\end{cases}}$ $\lim _{x\to \infty }{\sqrt[{x}]{x}}=1$ $\lim _{x\to \infty }{\sqrt[{N}]{x}}=\infty {\text{ for any }}N>0$ $\lim _{x\to \infty }\log x=\infty$ $\lim _{x\to 0^{+}}\log x=-\infty$ 