Pretty simple problem but I am not sure if the notation in my answer is correct -- So I am just going to post my answer and tell you what I am trying to say with it

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$\displaystyle f(x)=cosx/(1+cosx), x=(x)-[(x)in(Re) | 2(pi)n + (pi), (n)in(SetZ)$

Trying to say that x belongs to all real numbers excluding $\displaystyle pi $ rad and all of its similar angles.'

Was unable to figure out how to say some things in you equation maker so clarified below

in:Belongs to

pi:3.14159.....

Re: All Real Numbers

SetZ:Integer Set