Let $(X,\tau)$ be a [topological space](/page/Topological%20Space). Let $x,y \in X$, and let $\gamma : [0,1] \to X$ be a path from $x$ to $y$, where $[0,1]$ carries the [subspace topology](/page/Subspace%20Topology) inherited from $\mathbb{R}$. Define the map
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\begin{align*}
\overline{\gamma} : [0,1] \to X,\qquad t \mapsto \gamma(1-t).
\end{align*}
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Then $\overline{\gamma}$ is a path from $y$ to $x$.