ThmDex – An index of mathematical definitions, results, and conjectures.
P2388
For each integer $n \geq 1$, the function $f_n$ is a monomial restricted to the closed interval $[0, 1]$ and therefore continuous by the results
(i) R2923: Basic real polynomial function is continuous
(ii) R394: Domain-restriction of continuous map is continuous

Next, if $x \in [0, 1]$ and $n \geq 1$ is an integer, then \begin{equation} \lim_{n \to \infty} f_n(x) = \lim_{n \to \infty} x^n = \begin{cases} 1, \quad & x = 1 \\ 0, \quad & x \in [0, 1) \end{cases} \end{equation} Thus, if $ \varepsilon = 1/2$, then \begin{equation} |1 - f(x)| = |1 - 0| = 1 > \frac{1}{2} \end{equation} for all $x \in [0, 1]$ for which $0 < |1 - x|$. Thus, result R3312: Characterisation of continuity in Euclidean space states that $f$ is not continuous at $1$. $\square$