What does it mean to be be an inside or outside function?

Question

for example:
tell which is the inside function and which is the outside:
f(x)=sin3x

Answer 1

The idea is that
df (g(x) )/dx = df/dg * dg/dx
where f is the "outside function and g is the "inside" function
You do the outside function derivative first, then the inside function
so for your example we have
f ( g(x) ) = sin (g(x)) = sin ( 3x )
f (g) = sin g outside
g = 3x inside
so in your case
df/dg = cos g outside = cos 3x
dg/dx = 3 inside
so df/dx = cos g * 3
or 3 cos 3x