
  Opihi shell math operations:

  Mana will evaluate scalar (1D) arithmetic expresions in two
situations.  To set a variable equal to a math operation, use the
syntax is:

  $foo = expression

where "expression" is an arithmetic expression on numbers and
variables, including a variety of functions (see below).  After
performing the arithmetic and setting the variable to the resulting
value, mana returns the prompts without performing any further
command.  Mana will also evaluate any arithmetic expression enclosed
in curly brackets before attempting to perform the given command.  For
example, if the variables $MEAN and $SIGMA contain the mean and
standard deviation of an image, it would be possible to display the
image with a zero and range based on $MEAN and $SIGMA like this:

  tv image {$MEAN - 1.5*$SIGMA} {5*$SIGMA}


The two expressions in curly brackets are evaluated and the resulting
numbers passed as arguments to the "tv" command.

  See Also:  Variables, tv


list of valid math operations:

  binary operators:
  * (times)
  / (divided by)
  + (plus)
  - (minus)
  ^ (to the power of: 2^3 = 8)

  unary operators:
  exp (e to the power of)
  ten (10 to the power of)
  ln  (natural logarithm)
  log (log base 10)

  angles in radians:
  sin (sine)
  cos (cosine)
  tan (tangent)
  asin (arcsin)
  acos (arccos)
  atan (arctan)

  angles in degrees:
  dsin (sine)
  dcos (cosine)
  dtan (tangent)
  dasin (arcsin)
  dacos (arccos)
  datan (arctan)
