Question: Why are not subscripts appeared in the labels?

restart:
tf:=2:
n:=2:
X[1]:=t->t^2:
A[1]:=diff(X[1](t),t,t):
plot(A[1](t),t=0..tf,labels=["Time t","n times derivative of X[1](t)"]);

I have a code like above. I run it. Then,

in the labels; it was written "n times derivative of X[1](t)"] why not "2 times derivative of X[1](t)"]) ? and why was not the subscript appeared ? I mean that I want to see X1 instead of  X[1]?

Help me please.

Thank you.

 

Please Wait...