error using sym/subindex

Im trying to solve a problem bt suddenly I encountered a error in sym/subindex every time I try to run it

syms f(x) 

f(x)=sqrt(1-x^3)

f(x) = 

Volumen=pi*(int(f(x),[0,1]))^2

Volumen = 

Answer 1

[Torsten]

syms x
f(x) = sqrt(1-x^3);
V = pi* int(f^2,[0,1])