Solve SU(2) Parametrization Problem w/ Westra's PDF

[yoreh]

I have a trivial mathematical problem with SU(2) parametrization. In www.mat.univie.ac.at/~westra/so3su2.pdf , section 3, there is a sentence starting with "We first assume b = 0 and find then(...)". My question is: doesn't assuming that b = 0 reduce generality of our parametrization? If not, why?

 

[Fredrik]

What you need to do there is to consider two mutually exclusive possibilities separately. If b≠0, you can use a strategy that involves division by b. If b=0, that strategy doesn't work, but you can finish the problem without it.