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diff doc/interpreter/arith.txi @ 9155:ad20b967e1c9

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Update section 17.3 (Trigonometry) of arith.txi Add text to help strings to indicate which functions use radians and which use degrees. Add cross-references to radian function descriptions.
author Rik <rdrider0-list@yahoo.com>
date Sun, 26 Apr 2009 22:19:57 -0700
parents 761fc0d3d980
children 8c71a86c4bf4
line wrap: on
line diff
--- a/doc/interpreter/arith.txi
+++ b/doc/interpreter/arith.txi
@@ -103,7 +103,7 @@
 @node Trigonometry
 @section Trigonometry
 
-Octave provides the following trigonometric functions.  Angles are
+Octave provides the following trigonometric functions where angles are
 specified in radians.  To convert from degrees to radians multiply by
 @iftex
 @tex
@@ -113,7 +113,12 @@
 @ifinfo
 @code{pi/180}
 @end ifinfo
- (e.g., @code{sin (30 * pi/180)} returns the sine of 30 degrees).
+(e.g., @code{sin (30 * pi/180)} returns the sine of 30 degrees).  As
+an alternative, Octave provides a number of trigonometric functions
+which work directly on an argument specified in degrees.  These functions
+are named after the base trigonometric function with a @samp{d} suffix.  For
+example, @code{sin} expects an angle in radians while @code{sind} expects an
+angle in degrees.
 
 @DOCSTRING(sin)
 @DOCSTRING(cos)
@@ -143,22 +148,21 @@
 @DOCSTRING(acsch)
 @DOCSTRING(acoth)
 
-Each of these functions expects a single argument.  For matrix arguments,
-they work on an element by element basis.  For example,
+@DOCSTRING(atan2)
 
+Octave provides the following trigonometric functions where angles are
+specified in degrees.  These functions produce true zeros at the appropriate
+intervals rather than the small roundoff error that occurs when using
+radians.  For example:
 @example
 @group
-sin ([1, 2; 3, 4])
-     @result{}  0.84147   0.90930
-         0.14112  -0.75680
+cosd (90)
+     @result{} 0
+cos (pi/2)
+     @result{} 6.1230e-17
 @end group
 @end example
 
-@DOCSTRING(atan2)
-
-In addition to the trigonometric functions that work with radians,
-Octave also provides the following functions which work with degrees.
-
 @DOCSTRING(sind)
 @DOCSTRING(cosd)
 @DOCSTRING(tand)
@@ -193,6 +197,8 @@
 
 @DOCSTRING(ceil)
 
+@DOCSTRING(cross)
+
 @DOCSTRING(del2)
 
 @DOCSTRING(factor)
@@ -236,9 +242,9 @@
 @node Special Functions
 @section Special Functions
 
-@DOCSTRING(besselj)
+@DOCSTRING(airy)
 
-@DOCSTRING(airy)
+@DOCSTRING(besselj)
 
 @DOCSTRING(beta)
 
@@ -248,6 +254,10 @@
 
 @DOCSTRING(bincoeff)
 
+@DOCSTRING(commutation_matrix)
+
+@DOCSTRING(duplication_matrix)
+
 @DOCSTRING(erf)
 
 @DOCSTRING(erfc)
@@ -263,12 +273,6 @@
 @anchor{doc-gammaln}
 @DOCSTRING(lgamma)
 
-@DOCSTRING(cross)
-
-@DOCSTRING(commutation_matrix)
-
-@DOCSTRING(duplication_matrix)
-
 @node Coordinate Transformations
 @section Coordinate Transformations
 
@@ -283,16 +287,16 @@
 @node Mathematical Constants
 @section Mathematical Constants
 
+@DOCSTRING(e)
+
+@DOCSTRING(pi)
+
 @DOCSTRING(I)
 
 @DOCSTRING(Inf)
 
 @DOCSTRING(NaN)
 
-@DOCSTRING(pi)
-
-@DOCSTRING(e)
-
 @DOCSTRING(eps)
 
 @DOCSTRING(realmax)