A semi-circle, and the inverse semi-circle defined in terms of Y1:
Y1=√(100-X2) and Y2=-Y1
A parabola and the inverse parabola:
Y1=X2 and Y2=-X2
A sine wave and a cosine wave:
Y1=8sin(X) and Y2=8cos(X)
Y1=8tan(X)
Y1=√(X2) and Y2=-Y1
Y1=πX2 and Y2=-πX2
Y1=X-1 and Y2=-X-1
Y1=X2/X and -X2/X