We can use the Pythagorean theorem to solve this problem.
First, we find the length of the chord EG using the radius r and the diameter d:
d = 2r = 2(9 in) = 18 in
Next, we can find the length of the other leg of the right triangle formed by GF and EF:
EF^2 = EG^2 - GF^2
EF^2 = (18 in)^2 - (10.4 in)^2
EF^2 = 324 in^2 - 108.16 in^2
EF^2 = 215.84 in^2
Finally, we take the square root of both sides to find EF:
EF = sqrt(215.84 in^2)
EF = 14.69 in
Therefore, the measure of EF to the nearest inch is 15 inches.