# Toronto Math Forum

## MAT334--2020F => MAT334--Tests and Quizzes => Quiz 2 => Topic started by: Pengyun Li on October 01, 2020, 07:08:28 PM

Title: Quiz 2- Lec 5101-A
Post by: Pengyun Li on October 01, 2020, 07:08:28 PM
$\textbf{Question}$: Find the limit of each function at the given point, or explain why it does not exist: $f(z) = (z-2)log|z-2|$ at $z_0 = 2$.

$\textbf{Answer}$: Since $z_0= 2$, let $z' = z-2$.
$$\lim_{z\to z_0} f(z) = \lim_{z' \to 0} f(z) =z'\log |z'|$$
$$=z' (\ln |z'| +i\cdot 0) = \frac{ln |z'|}{\frac{1}{z'}}$$
By L'Hôpital's Rule, $$= \frac{\frac{1}{z'}}{-\frac{1}{(z')^2}}=\lim_{z'\to 0} (-z') = 0$$.

Therefore, the limit of the function is 0 at $z_0=2$.