Pluecker's conoid k=3

A variation on Pluecker's conoid, given by the parameterization x(s,t)=s*cos(t), y(s,t)=s*sin(t), z(s,t)=sin(3*t). Alternatively, by the function by z=f(x,y) = 3*y*(x^2-y^2)/(x^2+y^2)^(3/2). The function f(x,y)= 3*y*(x^2-y^2)/(x^2+y^2)^(3/2) has the property that f does not have a limit as (x,y) approaches (0,0) but it does have one sided limits when restricted to any line Ax+By=0 through the origin.