Closed nonorientable surface
= Closed nonorientable surface
A connected closed nonorientable surface of crosscap genus $k$ is the connected sum of $k$ real projective planes and has Euler characteristic $2-k$.
= Closed nonorientable surface
A connected closed nonorientable surface of crosscap genus $k$ is the connected sum of $k$ real projective planes and has Euler characteristic $2-k$.