Probability Density Functions in Fluid Mechanics

Hi all,

For an exam I'm required to be able to plot the PDF of a fluctuating velocity function, say u(t)=sint(wt), using what they call the "graphical technique", but handily I can't find it anywhere in the lecture notes, and I'm struggling to find anything with a standard Google search.

Does anyone know an online resource or otherwise where I can learn this?

Cheers,
pobatso.