Okay,

I am studying maths at a university (home study)

I cant get my head around sine waves. Right, this is what I know:

A sine-wave is called a sine wave because if we stick a triangle in a circle and make it go round and round and compare anan angle of a triangle in the circle to the height of one of the sides as it goes round and round and plot all of these differences on a graph, we will get a bouncy up and down wave which we call a "sine wave".

Okay great, I dont see any useful application for this - if you plot radio frequency, or a clean sound frequency on an oscilloscope you will also get a "sine wave", but what that got to do with triangles and circles?

and why the circle and triangle in the first place? :S