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## Creating Equations

Although there is an equation editor in PowerPoint, it is not very powerful, and lacks such rudimentary features as the ability to change the colours of the equation. Showcase has no equation editor at all. However, there is fortunately a simple solution to this. There are two programs on the SGI, one called equationtopict, and the other equationtorgb.

As might be expected, equationtopict creates a Macintosh PICT from an equation description, while equationtorgb creates an IRIS RGB. The equation description is identical to that used in LaTeX. Please see the LaTeX documentation for further details on how to describe equations. As an example, the following description of an equation could be saved in a file called equation.tex:

S_{xx} = \frac{1}{2} \left( \frac{\partial u_x}{\partial
x} + \frac{\partial u_x}{\partial x} \right) = K

which corresponds to the expression:

Please note that the input file to equationto* contains only the equation description. It does not contain any other LaTeX commands.

The colours of the equation are specified on the command line to equationto*. Colour specifications follow the format specified in the manual page for pgmtoppm. Type man pgmtoppm for further details. Basically the colours are specified using their red, green, and blue components. Unfortunately, the value of these components is specified in hexadecimal notation, which is more difficult for those of us without 16 fingers. For example, to create an RGB of the above equation with a black background and yellow foreground:

equationtorgb equation.tex equation.rgb #FFFF00 #000000

where #FFFF00 represents yellow, and #000000 represents black.

Mark Wolforth (wolforth@bic.mni.mcgill.ca)