Drag the top layer to perform calculations.
Follow the black lines to read the real part of a number, and follow the red lines to read the imaginary part.
Unlike an ordinary slide rule, this one also contains negative numbers (indicated by overline)
Press T to show only the top layer (you will also see the z=1 point of the bottom layer).
Press B to show only the bottom layer (you will also see the z=1 point of the top layer).
Tip: maximize your browser window (F11)
See Complex number slide rules
This help panel will disappear when you start dragging the top layer. Press ? to redisplay this panel.