Let p be a point of S and P be a neighbourhood of p . Let S , T be non empty topological spaces and f be a map from S into T . Then f is open. Let S , T be non empty topological structures and f be a map from S into T . Let S , T be non empty topological structures and f be a map from S into T .
P is open.
Let S , T be non empty topological structures and f be a map from S into T . Let S be a topological space, T be a non empty topological space, and f be a map from S into T . Let T be a non empty topological space. Note that there exists a subset of T which is non empty and dense. If f is a homeomorphism, then f A is dense.