Hello,
When you compose 2 reciprocals functions, you will find 1.
ex f(x)=√x and g(x)=x² , x>=0
so that g(f(x))=(√x)²=x
sin(cos(0))=sin(1)=0,84147... rad and not 1.
Reciprocal function of sin (x) is arcsin(x).
Reciprocal function of cos (x) is arccos(x).