What Does T=D+D\circ D Represent in Polynomial Vector Spaces?

[transgalactic]

what this circle mean??

v is vectoric space of all polinomials <=3 with coefficient of R
D:v->v
T:v->v
i need to find the operator of
$$T=D+D\circ D$$

find T regarding b={1,t,t^2,t^3} of V

 

[Mark44]

It usually means composition. For example, $(f \circ g)(x)$ is f(g(x)).