lib/toxi/geom/vectors.js
function(theta) {
			var co = Math.cos(theta);
			var si = Math.sin(theta);
			var xx = co * this.x - si * this.y;
			this.y = si * this.x + co * this.y;
			this.x = xx;
			return this;
		}
function(theta) {
			var co = Math.cos(theta);
			var si = Math.sin(theta);
			var xx = co * this.x - si * this.y;
			this.y = si * this.x + co * this.y;
			this.x = xx;
			return this;
		}
function ( theta ) { var co = Math . cos ( theta ) ; var si = Math . sin ( theta ) ; var xx = co * this . x - si * this . y ; this . y = si * this . x + co * this . y ; this . x = xx ; return this ; }
Rotates the vector by the given angle around the Z axis.

@param theta
@return itself
Rotates the vector by the given angle around the Z axis .