If you want
to find the derivative of the function
f at the input 2, for example, you'd enter d (f(x),x)|x=2.
(First,
you'd have to define the function f. d
( is 2nd 8, not the letter d.)
In most cases,
the calculator executes the command to the left of the with bar
and imposes the condition after the with bar.
Sometimes
the condition takes effect too early. In that case, enter the command without
the with bar, and then enter ans(1)|[whatever your condition
is].
(ans(1)
is 2nd (-) at the bottom of the numeric keypad.)
The condition after the with bar should be of the form variable = value or inequalities like variable < value. Assigning values to complicated expressions rather than simple values usually doesn't work. The calculator doesn't accept |f(2)=3, for example.
You can impose several conditions at once if you separated them by and.