Muestra que si f es la función que encaja a $S^{1}$ en la circunferencia que rodea al cilindro mayor, por la mitad, de la casa de Bing, entonces f es homotópica a una constante.
Show that if $\,f\,$ is the function embedding $\,S^1\,$ in the circumference around the main cylinder, at its half, of Bing's House, then $\,f\,$ is homotopic to a constant.
Here is the description of this space from page 4 of Hatcher's Algebraic Topology: