Posted by sara on .
NEED HELP WITH ONLY PART C
Two 135.1.0W speakers, A and B, are separated by a distance D = 3.6 m. The speakers emit inphase sound waves at a frequency f = 11800.0 Hz. Point P1 is located at x1= 4.50 m and y1 = 0 m; point P2 is located at x2 = 4.50 m and y2 = –y.
a) Neglecting speaker B, what is the intensity, IA1 (in W/m2), of the sound at point P1 due to speaker A? Assume that the sound from the speaker is emitted uniformly in all directions.
b) What is this intensity in terms of decibels (sound level, ßA1)?
c) When both speakers are turned on, there is a maximum in their combined intensities at P1. As one moves toward P2, this intensity reaches a single minimum and then becomes maximized again at P2. How far is P2 from P1, that is, what is ?y? You may assume that L >> y and that D >> y, which will allow you to simplify the algebra by using (a±b)1/2 ˜ a1/2 ± 0.5b/a1/2 when a >> b.

physics 
bobpursley,
I don't see any indicaton of the x,y coordinates of the speakers.