A differential geometry question.

[binglee]

Fix a number L > 2. Consider all smooth plane curves r of length L that connect (−1, 0) and (1, 0) and are contained in the upper half-plane. Note that and the segment [−1, 1] of the X-axis together bound a plane domain D. Find r such that D has the maximal possible area.

 

[Hurkyl]

Sounds like a homework problem. You know we aren't an answer service, right?