This is my first post in this forum, i have scimmed the rules and tried to find the correct place to this post, my problem is that i'm not studying math in english so i'm not quite sure if this question should be in another forum.
I wanna show that if i have C_1,...,C_m convex subgroups of R^2 where the unity of every group of three is nonempty the unity of them all is nonempty, preferebly the proof should be by induction.
I hope some of you are willing to help!
p.s. I cannot get that fancy math thing to work, how do i do that?