Two sound sources radiating in phase at a frequency of 500 Hz interfere such that maxima are heard at angles of 0° and 27° from a line perpendicular to that joining the two sources. The listener is at a large distance from the line through both sources, and no additional maxima are heard at angles in the range 0° < θ < 27°. Find the separation d between the two sources, and any other angles at which intensity maxima will be heard. Use the following result.