# Math Insight

### Applet: A change of variables for an electrode tip domain

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A change of variables $\cvarf$ maps a rectangular solid $\dlv^*$ (first panel) onto the electrode tip $\dlv$ (second panel). You can explore the mapping by moving with the mouse the red point in $\dlv^*$, which represents the point $(\cvarfv,\cvarsv,\cvartv)$, or the point blue point in $\dlv$, which represents the point $(x,y,z)$. When you move one point, the other point moves to reflect the mapping so that $(x,y,z)= \cvarf(\cvarfv,\cvarsv,\cvartv)$.

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#### General information about three.js applets

The applet was made using three.js and requires Javascript as well as a browser that supports WebGL. For most three.js applets, you can drag with the mouse to rotate the view, drag with the right button to pan, and zoom in/out with the mouse wheel. Many applets contain points that you can drag to change values of variables.