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L'Hospital's Rule

*used to handle indeterminate forms of a limit

Indeterminate Forms

00\frac{0}{0}, ∞∞\frac{\infty}{\infty}, 0×∞0\times\infty, ∞−∞\infty-\infty, 1∞1^{\infty}, ∞0\infty^0, 000^0

L'Hopital's Rule

Criteria:
  • ff and gg are differentiable and g′(x)≠0g'\left(x\right)\ne0 and
  • lim⁡x→af(x)g(x)=00   or   ±∞±∞\lim_{x\to a}\frac{f\left(x\right)}{g\left(x\right)}=\frac{0}{0}\ \ \ or\ \ \ \frac{\pm\infty}{\pm\infty}
Then lim⁡x→a f(x)g(x)=lim⁡x→a f′(x)g′(x)\lim_{x\to a}\ \frac{f\left(x\right)}{g\left(x\right)}=\lim_{x\to a}\ \frac{f'\left(x\right)}{g'\left(x\right)}.

Other Indeterminate forms


Practice: L'Hospital's Rule

Determine lim⁡x→0tan⁡xex−1\displaystyle \lim_{x\rightarrow0}\frac{\tan x}{e^x-1}.

Practice: L'Hospital's Rule

Evaluate lim⁡x→∞ x3 sin⁡(1x2)\displaystyle \lim_{x\to\infty}\ x^3\ \sin\left(\frac{1}{x^2}\right).

Practice: L'Hospital's Rule

Evaluate lim⁡x→0+(e1x)1ln⁡x\lim_{x\rightarrow0^+}\left(e^{\frac{1}{x}}\right)^{^{\frac{1}{\ln x}}}.