where 
represents the disturbance caused by the wave (e.g. a transverse displacement) at position 
and time 
and the constants 
and 
are the amplitude, angular wavenumber, propagation speed and phase constant respectively. [M6.4, P5.6]
is: a periodic wave described (in one spatial dimension) by a function of two variables of the form where represents the disturbance caused by the wave (e.g. a transverse displacement) at position and time and the constants and are the amplitude, angular wavenumber, propagation speed and phase constant respectively. [M6.4, P5.6]
may be generalized: to two or three dimensions, and may be represented mathematically in a variety of different ways e.g. using complex numbers, 
where 
[M6.4, P5.6]
can be represented: by the cosine function as well. By writing 
and using an appropriate trigonometric identity it is possible to rewrite the 'sine wave' given above as the 'cosine wave' 
[M6.4, P5.6]
Copyright 1997, The Open University