Product of connected spaces (source code)

= Product of connected spaces

The product of any family of connected spaces is connected. For two factors, fix $y_0$ and use the connected sets
$$
(X\times\{y_0\})\cup(\{x\}\times Y),
\qquad x\in X.
$$
They cover $X\times Y$ and all contain the connected horizontal slice $X\times\{y_0\}$.