They don't give you the equation for visual angle? I'd imagine it would be the arc-tangent of (9/x), or some such relation like that. Perhaps there is a specific equation you are meant to use.
A tapestry 7 feet high hangs on a wall. The lower edge is 9 feet above the observer's eye. How far from the wall should the observer stand to obtain the most favourable view? That is, what distance from the wall maximizes the visual angle of the observer?
"visual angle"?? what? Would appreciate if someone guide me through this problem thanks.