HP 50g Graphing Calculator - Manual (Page 822)

Page C-11
Notice that, in this instance, soft menu keys E and F are the only one with
associated commands, namely:
!!CANCL E CANCeL the help facility
!!@@OK#@ F OK to activate help facility for the selected command
If you press the !!CANCL E key, the HELP facility is skipped, and the calculator
returns to normal display.
To see the effect of using !!@@OK#@ in the HELP facility, let’s repeat the steps used
above from to the selection of the command ATAN2S in the list of CAS
commands:
@HELP B` ˜ ˜ …(10 times)
Then, press the !!@@OK#@ F key to obtain information about the command
ATAN2S.
The help facility indicates that the command, or function, ATAN2S replaces the
value of atan(x), the arc tangent of a value x, by its equivalent in terms of the
function asin (arcsine), i.e.,
The fourth and fifth lines in the display provide an example of application of the
function ATAN2S. Line four, namely, ATAN2S(ATAN(X)), is the statement of the
operation to be performed, while line five, namely, ASIN(X/
√(X^2+1)), is the
result.
The bottom line in the display, starting with the particle See:, is a reference line
listing other CAS commands related to the command ATAN2S.