I have half a circle and do not know diameter, however i do know the length from point a to point b which is 34 feet. How can I determine the square footage of a half circle if I don't know the diameter?

Question

I have half a circle and do not know diameter, however i do know the length from point a to point b which is 34 feet.  How can I determine the square footage of a half circle if I don't know the diameter?

anonymous · Answer

what's square footage and are points a and b anywhere on the half circle?

anonymous · Answer

i have added an attachment.  There is 34 feet between point a and point b

anonymous · Answer

i can't find the area of the circle with only this line ._.
sorry