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

It is a property of power rule, used to find the limit of an exponential function whose base and exponent are in a function form.

$x$ is a variable and two functions $f{(x)}$ and $g{(x)}$ are defined in terms of $x$. The limits of $f{(x)}$ and $g{(x)}$ as $x$ closer to $a$ are written mathematically in calculus as follows.

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

$(2) \,\,\,\,\,\,$ $\displaystyle \large \lim_{x \,\to\, a}{\normalsize g{(x)}}$ $\,=\,$ $g{(a)}$

Assume, the functions $f{(x)}$ and $g{(x)}$ are formed a function in exponential form.

${f{(x)}}^{g{(x)}}$

Now, find the limit of this exponential function as $x$ approaches $a$.

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

Find the limit of the exponential function by substituting $x$ by $a$.

$= \,\,\, {f{(a)}}^{g{(a)}}$

The limits of functions $f{(x)}$ and $g{(x)}$ as $x$ tends to $a$ are $f{(a)}$ and $g{(a)}$ respectively. Therefore, it can be written that $f{(a)}$ and $g{(a)}$ as the limits of functions $f{(x)}$ and $g{(x)}$ respectively.

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

Actually, the value of $f{(a)}$ is raised to the power of $g{(a)}$ is determined as the limit of the $f{(x)}$ is raised to the power of $g{(x)}$ as $x$ closer to $a$.

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

Therefore, the limit property is proved that the limit of $f{(x)}$ is raised to the power of $g{(x)}$ as $x$ approaches $a$ equals to the limit of $f{(x)}$ as $x$ approaches $a$ is raised to the power of the limit of $g{(x)}$ as $x$ closer to $a$.

The limit rule is completely in exponential notation. So, it is called as the power rule of limit in calculus.

Latest Math Topics

Latest Math Problems

Email subscription

Math Doubts is a best place to learn mathematics and from basics to advanced scientific level for students, teachers and researchers.
Know more

Learn how to solve easy to difficult mathematics problems of all topics in various methods with step by step process and also maths questions for practising.