From 38468bfbd053e18201425db14c7e910538a1c369 Mon Sep 17 00:00:00 2001
From: Simon Budig <simon@budig.de>
Date: Fri, 11 Aug 2017 03:36:55 +0200
Subject: [PATCH] 3d-function-8.tex: convert argument of sin() to degrees.

tikz apparently expectes the argument to sin() in degrees. This is in
strong contrast to the usual conventions in math, where the argument is
expected in radians.

With this example it actually provides a bogus graph - it actually
should approach f(x,y) = 1 for large x and y (since 1/(x^2+y^2) is
small for large x,y; hence sin(1/(x^2+y^2)) can be approximated by
1/(x^2+y^2), resulting in f(x,y) -> 1 for large x,y).

Also I've adjusted the plot range a bit, since this then actually shows
the "interesting" center of the function (x=y=0).
---
 tikz/3d-function-8/3d-function-8.tex | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tikz/3d-function-8/3d-function-8.tex b/tikz/3d-function-8/3d-function-8.tex
index 867c3f9..3e74a62 100644
--- a/tikz/3d-function-8/3d-function-8.tex
+++ b/tikz/3d-function-8/3d-function-8.tex
@@ -18,8 +18,8 @@
     view={65}{65},
     enlargelimits=false,
     grid=major,
-    domain=-5:5,
-    y domain=-5:5,
+    domain=-1:1,
+    y domain=-1:1,
     samples=50, %57 : TeX capacity exceeded, sorry [main memory size=3000000].
                 % see also http://tex.stackexchange.com/a/7954/5645
     xlabel=$x$,
@@ -33,7 +33,7 @@
         title={$f(x,y)$}
     }
     ]
-      \addplot3[surf] {(x^2+y^2)*sin(1/(x^2+y^2))};
+      \addplot3[surf] {(x^2+y^2)*sin(deg (1/(x^2+y^2)))};
     \end{axis}
 \end{tikzpicture}
 \end{preview}