Another way to solve the one-dimensional wave equation is to first analyze its frequency eigenmodes. A so-called eigenmode is a solution that oscillates in time with a well-defined constant angular frequency ω, so that the temporal part of the wave function takes the form e = cos(ωt) − i sin(ωt), and the amplitude is a function f (x) of the spatial variable x, giving a separation of variables for the wave function: u ω ω ( x , t ) = e − − i ω ω t f ( x ) .