I don't understand how does $ \epsilon $ come at the end of this formula in article from Wikipeida
\begin{align} \left | \frac{1}{2 \pi i} \oint_C \frac{f(z)}{z-a} \,dz - f(a) \right | &= \left | \frac{1}{2 \pi i} \oint_C \frac{f(z)-f(a)}{z-a} \,dz \right |\\[.5em] &\leq \frac{1}{2 \pi} \int_0^{2\pi} \frac{ |f(z(t)) - f(a)| } {\varepsilon} \,\varepsilon\,dt\\[.5em] &\leq \max_{|z-a|=\varepsilon}|f(z) - f(a)| \xrightarrow[\varepsilon\to 0]{} 0. \end{align}$ \frac{1}{2 \pi} \int_0^{2\pi} \frac{ |f(z(t)) - f(a)| } {\varepsilon} ,\varepsilon \text{ (<--this epsilon) }\,dt $ And also $dz$ is changed in to $dt$ shouldn't there be something to balance it.?