Jan 3 2012

## Snow White

For those of you who doesn’t know Linear Algebra (yet…), the matrix on the blackboard is a reflection matrix, when multiplying with a $\mathbb R^{2}$ vector, the matrix will change the sign of the x coordinate, therefor it will create a reflected image of the vector.

Jan 2 2012

## Q wants to break free!

Today in Algebraic structures class we’ve learned about free groups. And learned that $\mathbb Q$ (the rationals) is not a free group…

Dec 23 2011

## Bug in LyX for Mac – \Omega, \otimes are not being displayed on designer

If you are using LyX on mac you probably noticed that some symbols are missing while editing an equation.

One of the symbols missing is $\Omega$ which is really annoying when you learn probability.
When you try and type \Omega, instead of seeing the symbol you will just see a blank space.

I’ve dived into the code, and found out how the all designer works. For most of the symbols, the translation is quite simple. There are several font files, and a file named symbols (located in /Application/LyX.app/Contents/Resources) which maps every latex code to the relevant font and unicode value.

The problem with $\Omega$ and $\otimes$ is that their unicode value is 0x00ad. And as it seems, QT4 has bug with characters with that code. LyX source code mentioned this bug in GuiPainter.cpp and it have some code to try and fix it, but for some reason it doesn’t work.

A work around for the $\Omega$ is to make a small change in the symbols file, locate the Omega line (with capital O) and change the code from 173 to 937 (a code for different Omega character that is available in the font).

I didn’t find (didn’t really looked for) a way to fix the \otimes, because i don’t really use it. A way to fix it will be using a font editor and changing the font and map the wanted symbols from other unused code. Again, didn’t care enough to do it, If someone want me to just post here. But I believe that LyX developers will soon enough fix it.