Hint: The angle may be too large to use small angle approximation.
Sound waves of frequency 567 Hz enter a window 1.1 m wide. The window is in the exact center of one wall of a theater 24 m by 12 m. The window is 12 m from the opposite wall, along which is a row of seats occupied by people. The theater is acoustically prepared to prevent the reflection of sound waves, and the speed of sound is 330 m/s. Two people, on each side of a line directly in front of the window, in the row along the wall hear no sound.
What minimum distance are they from each other? Answer in units of m.