So this is an assigned problem, but I can assure you that I have tried this problem multiple times and still seem to get the incorrect answer.
If we suppose the unknown rate of change in the angle as z...
x/8 = tan z
x = 8 tan z
dx/dt = 8 sec(z)^2 * dz/dt
dz/dt = 1/8 cos(z)^2 * dx/dt
dz/dt = 1/8 cos(z)^2 * 1.3
dz/dt = 1.3/8 cos(z)^2
dz/dt = 1.3/8 (8/10)^2 <-- cos(z) is 8/10
dz/dt = 1.3/8 (64/100)
dz/dt = 0.104 rad/s
But it still says I'm wrong...? I've done the problem from the beginning a few times, and I still get the same answer. HELP!