Y by Mango247
The plane shows
straight lines in general position, that is, there are none three intersecting at one point but no two parallel. Let's say, that the drawn line
detaches the drawn line
if all intersection points of line
with the other drawn lines lie in one half plane wrt to line
(given the most straightforward
). Prove that you can be guaranteed find two drawn lines
and
that
detaches
, but
does not detach
.











