# Prevent Simplify from using cot

I have the following problem. I got a huge equation to simplify and in there are numerous $$\cos(x)$$ and $$\sin(x)$$ terms and now it happens that Simplify changes terms like $$(...+\cos(x)*a+...)$$ to $$(...+\cot(x)*a+...)*\sin(x)$$. I don't know why it does that but because $$\cot$$ got a pole at $$\sin(x)=0$$, while the actual equation does not, I cant translate that equation any more to C code and implement it because it will cause awkward errors. Anyone got an idea about that behaviour and how to get rid of it?

Thanks..

• Do you get the desired result if you use the option Trig -> False, i.e., Simplify[yourexpression,Trig -> False]?
– kglr
Dec 21, 2014 at 14:47
• Yes,it does not change the trigonometric functions any more. But is there a way to set this parameter from within Collect? Cause I call it like that: Collect[expr,a,Simplify]... Dec 21, 2014 at 15:01

Collect[expr, a, Simplify[#, Trig -> False] &]