This Demonstration uses two logarithmic grids to compute the product of two complex numbers, which is analogous to the way a slide rule uses two logarithmic scales. Move the point with the double blue circles to set the value of the first factor . Move the point with the purplish circle to set the value of the second factor . The second point has two values corresponding to it. Its value on the purplish grid is and its value on the blue grid is the product . Values are displayed near the points in their respective colors. You can also treat the double-circled point as the quotient of the values of the single-circled point on the grids, the blue divided by the purple.
The magnetic grid option makes the point snap to a nearby grid intersection when the point is close enough. When the multiplication option is selected and the double-circled blue point is dragged, it snaps to the blue grid. When the division option is selected and the blue point is dragged, it snaps so that the single-circled purplish point aligns with a blue grid intersection. (This helps select simple values when exploring division.) When moving the purplish point with the magnetic grid option selected, the point always snaps to the purplish grid or its extension.
Note that you can drag the purplish point beyond its grid.