You know, as soon as I saw it in Sub9 Theories, I wanted to go Off-Topic because I'm racking my brain looking for what it is...and I'm not ready to google it.I got a mathignature as well.
I'm going to take a guess or two: It's either Torque...which it's not, since it's 2 Pi. Or...you know, I'm reminded of something about Sine, Cosine and Tangent, the height of the graph. Am I close?