1. The problem statement, all variables and given/known data acos(x)+bsin(x)=Rsin(x+t) 2. Relevant equations 3. The attempt at a solution Is there any way to show how R is "placed" in acos(x)+bsin(x)=Rsin(x+t) algebraically? I mean I could, probably, do acos(x)+bsin(x)=sin(t)cos(x)+ cos(t)sinx(x), but still somehow need R in it. Does R give the equation more balance? ;) Well, we also have x=Rcost and y=Rsint in addition to double angle identities, but I still can't seem to find satisfying algebraic justification for R's existence in f(x)= Rsin(x+t). Please, help me figure it out. Thanks.