I know this is probably simple but I just can't see it.
How can I determine the scale factor of a pantograph from the ratio of the arms?
I know this is probably simple but I just can't see it.
How can I determine the scale factor of a pantograph from the ratio of the arms?
The scale factor is the ratio $\frac{\text{distance from the fixed point to the drawing point}}{\text{distance from the fixed point to the tracing point}}.$ The mechanics of the device serve to keep that ratio constant as the mechanism is rotated, expanded, and/or contracted.
This page breaks down the triangles pretty well.