Light effects: Need help!
 

The most i've done with light effects is the flickering of lanterns and a really basic fading shield. I'm not a whiz at mathematics/operations by any means and I have no idea where to start.

Basically, what I want with this effect is for lights to hover around the player and dance, like fairies of such. I cant, however, think of any mathematical operation that'd loop to a certain value then jump into the minuses so my knowledge can transpose that into a backwards movement.

A lot of help here would be brilliant. I learn best off snippets.

sine? cosine?

Sin(1.57) = 1
Sin(3.14) = 0
Sin(4.61) = -1
Sin(6.28) = 0
Sin(7.85) = 1
Sin(9.42) = 0
Sin(10.99) = -1

See a pattern?