Two sounds of equal amplitude and frequencies, `n_(1)` and `n_(2)`, reach a point together. The resultant wave can have which of the following forms (symbols have their usual meanings) ?

Options

A. `y = A sin [((n_(1) - n_(2))/(2))t] sin [((n_(1) + n_(2))/(2))t]`
B. `y = A cos [((n_(1) - n_(2))/(2))t] cos [((n_(1) + n_(2))/(2))t]`
C. `y = A sin [(n_(1) - n_(2))t] cos [(n_(1) + n_(2))t]`
D. `y = A sin [(n_(1) - n_(2))t] sin [((n_(1) + n_(2))/(2))t]`

Answer

A, B