# 
restart;
with(plots);
f:=x->sec(x);
a:=0;
b:=Pi/4;
plot(f(x),x=a..b,y=0..4,
    scaling=constrained);
top:=plot3d([x*cos(theta),f(x),x*sin(theta)],
    x=a..b,theta=0..2*Pi):
bot:=plot3d([x*cos(theta),0,x*sin(theta)],
    x=a..b,theta=0..2*Pi):
display([top,bot],scaling=constrained);
V:=Int(2*Pi*x*f(x),x=a..b);
evalf(V);
Digits:=20;
evalf(V);
?dilog
plot(dilog(x),x=0..300);
limit(dilog(x),x=infinity);

#