Here is a link to see if this will help you, just fill in the blanks and see how this goes.
http://www.handymath.com/cgi-bin/arc18.cgi?submit=Entry
One other point, square inches are just multiplying the 2 dimensions. Your question 10.9" x 5" if both lines were parallel would equal 54.5. So since one is on a radius it would be cutting off some of the area. So as a quick reference you can use this square method knowing it will get you close. This is the best I could do with out knowing the diameter of you CC.
jm2cw