The pantograph will also give us the average of two complex numbers. That is, given both y and z, complex numbers, we can get w=(y+z)/2 by not anchoring our linkage at all, and by labeling the middle vertex (of the 3 collinear vertices) w, and the two on either side of it with y and z.



How would we get sum from average?

Hint: think about the function, not so much about the linkages.