Is it possible to cut unit disk in more than 8 parts of equal area (possibly not congruent) by 4 lines?
It's can be proved that it's impossible to cut circle in 7 parts by 3 lines. For example, here is proof - Dividing a disk into $7$ equal pieces with $3$ line segments .
My question is about what we can do with 4 lines.
So conjecture is that maximum number of parts of equal area for $n$ lines is $2n.$