# 
restart;
f:=x->2+ln(x)*sin(3*x);
plot(f(x),x=1..4,scaling=constrained);
plot3d([x,f(x)*cos(theta),f(x)*sin(theta)],x=1..4,theta=0..2*Pi,scaling=constrained);
V:=int(Pi*f(x)^2,x=1..4);
int(Pi*f(x)^2,x);
Int(Pi*f(x)^2,x);
evalf(V);
+
#