I'm trying to find the formula to get the area as a function of that length....

So far I got

Area =

1/2[sq. root(2L^2)][sq. root(L^2 - [(sq. root((2L^2)/2)]^2)] + [pi([(sq. root((2L^2)/2)^2]]/2

The question asks...find the length of l for area 30 cm^2