Math Doubts

Properties of Limits

There are some fundamental properties in limits. They are used as formulas in some basic operations and also used in evaluating limits of the functions in calculus.

Operations

The list of fundamental operations of limits with their formulas and proofs.

$(1)\,\,\,$ $\displaystyle \large \lim_{x \,\to\, a}{\normalsize \Big[f(x)+g(x)\Big]}$ $\,=\,$ $\displaystyle \large \lim_{x \,\to\, a}{\normalsize f(x)}$ $+$ $\displaystyle \large \lim_{x \,\to\, a}{\normalsize g(x)}$

$(2)\,\,\,$ $\displaystyle \large \lim_{x \,\to\, a}{\normalsize \Big[f(x)-g(x)\Big]}$ $\,=\,$ $\displaystyle \large \lim_{x \,\to\, a}{\normalsize f(x)}$ $-$ $\displaystyle \large \lim_{x \,\to\, a}{\normalsize g(x)}$

$(3)\,\,\,$ $\displaystyle \large \lim_{x \,\to\, a}{\normalsize \Big[f(x) \times g(x)\Big]}$ $\,=\,$ $\displaystyle \large \lim_{x \,\to\, a}{\normalsize f(x)}$ $\times$ $\displaystyle \large \lim_{x \,\to\, a}{\normalsize g(x)}$

$(4)\,\,\,$ $\displaystyle \large \lim_{x \,\to\, a}{\normalsize \dfrac{f(x)}{g(x)}}$ $\,=\,$ $\dfrac{\displaystyle \large \lim_{x \,\to\, a}{\normalsize f(x)}}{\displaystyle \large \lim_{x \,\to\, a}{\normalsize g(x)}}$

Constant multiple

The limit of product of a constant and a function is equal to product of that constant and limit of the function.

$\displaystyle \large \lim_{x \,\to\, a}{\normalsize \Big[k.f{(x)}\Big]}$ $\,=\,$ $k \times \displaystyle \large \lim_{x \,\to\, a}{\normalsize f{(x)}}$

Reciprocal rule

The limit of reciprocal of a function is equal to reciprocal of limit of the function.

$\displaystyle \large \lim_{x \,\to\, a}{\normalsize \dfrac{1}{f(x)}}$ $\,=\,$ $\dfrac{1}{\displaystyle \large \lim_{x \,\to\, a}{\normalsize f(x)}}$

Exponentiation

The limit of an exponential function is equal to exponentiation of their limits.

$\displaystyle \large \lim_{x \,\to\, a}{\normalsize {f{(x)}}^{g{(x)}}}$ $\,=\,$ $\displaystyle \large \lim_{x \,\to\, a}{\normalsize {f{(x)}}^{\, \displaystyle \large \lim_{x \,\to\, a}{\normalsize g{(x)}}}}$

Composition

The limit of composition of two functions is equal to the value of the function for the limit of its internal function.

$\displaystyle \large \lim_{x \,\to\, a}{\normalsize f{(g{(x)})}}$ $\,=\,$ $f{\Big(\displaystyle \large \lim_{x \,\to\, a}{\normalsize g{(x)}}\Big)}$

Formulas

List of standard results of limits with proofs to use them as formulas in calculus.

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