stationary waves, urgent! helllloo. i'm having a major exam tomorrow and i stumbled across this question just now..would appreciate all your help! Two loudspeakers S1 and S2 are placed a distance 4.0m apart facing each other. The loudspeakers produce sound waves of frequency 165 Hz in phase with one another. A microphone, connected to a CRO, is moved along a straight line joining S1 and S2. The sound received by the microphone fluctuates regularly. Speed of sound is 330m/s. (ii) Find the shortest distance from S1 where a minimum intensity is detected. I understand that a stationary wave is formed between the 2 speakers and what this question requires is the distance of the first node from S1. Not too sure on how to get there though.. the answer key provided just drew 2 cosine waves from S1 to S2, one negative and the other positive. since the wavelength is 2.0m, the min. intensity is detected at 0.5m.. what i dont understand is how and why the cosine waves are derived, why not sine waves? thanks!