Angular Modes
-------------

The Calculator supports three notations for angles: radians, degrees,
and degrees-minutes-seconds.  When a number is presented to a function
like `sin' that requires an angle, the current angular mode is used to
interpret the number as either radians or degrees.  If an HMS form is
presented to `sin', it is always interpreted as
degrees-minutes-seconds.

Functions that compute angles produce a number in radians, a number in
degrees, or an HMS form depending on the current angular mode.  If the
result is a complex number and the current mode is HMS, the number is
instead expressed in degrees.  (Complex-number calculations would
normally be done in radians mode, though.  Complex numbers are
converted to degrees by calculating the complex result in radians and
then multiplying by 180 over `pi'.)

The `m r' (`calc-radians-mode'), `m d' (`calc-degrees-mode'), and `m
h' (`calc-hms-mode') commands control the angular mode.  The current
angular mode is displayed on the Emacs mode line.  The default angular
mode is degrees.