"Sorry"? Try "Haha"!

( Gee, if we all have to be worried about making mistakes then we may as well take the "Fun" off the forum name. )

Still not quite there ... maybe i am not getting my formula right.

=900*PI()*ACOS(B8/60) + B8*B8*PI() *ACOS(1-B8*B8/1800) - SQRT((30+B8/2) * (B8/2)* (B8/2) * (30-B8/2))

If you have a chance, see if you can get it working, then just delete the last two or three posts and show the world how neat and perfect we are!