Question: extracting one solution

I am having trouble extracting one part of a return of a solve.


> relatie := CD^2 = (AB+BC*cos(beta)+AD*sin(alpha))^2+(BC*sin(beta)-AD*cos(alpha))^2;
> vergelijking := solve(relatie, beta);
the solve seems to return 4 expresions and the data type is exprseq. I only need the first expresion (till the first comma) I tried using temp:=vergelijking[1] but that still contains 2 parts separated by a comma.
Is it a substring of some kind? how do I just extract the first part?
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