[goffice] Math: improve sinpil/cospil/tanpil/cotpil.

[Morten Welinder <mortenw src gnome org>]

commit ca0a1c01e1e890e912ac62d77c513d82d933754a
Author: Morten Welinder <terra gnome org>
Date:   Tue Mar 6 21:15:56 2018 -0500

    Math: improve sinpil/cospil/tanpil/cotpil.

 ChangeLog              |    5 +++++
 NEWS                   |    3 +++
 goffice/math/go-math.c |    2 +-
 3 files changed, 9 insertions(+), 1 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 9586f0d..5236b50 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2018-03-06  Morten Welinder  <terra gnome org>
+
+       * goffice/math/go-math.c (do_sinpil): Improve accuracy of
+       fallback.
+
 2018-02-14  Jean Brefort  <jean brefort normalesup org>
 
        * goffice/canvas/goc-image.c (goc_image_draw): don't try to display an image
diff --git a/NEWS b/NEWS
index 7ec2ab5..f8f737b 100644
--- a/NEWS
+++ b/NEWS
@@ -1,5 +1,8 @@
 goffice 0.10.39:
 
+Morten:
+       * sinpi/cospi/tanpi/cotpi improvement.
+
 --------------------------------------------------------------------------
 goffice 0.10.38:
 
diff --git a/goffice/math/go-math.c b/goffice/math/go-math.c
index e2bad63..22d7a9e 100644
--- a/goffice/math/go-math.c
+++ b/goffice/math/go-math.c
@@ -1126,7 +1126,7 @@ do_sinpil (long double x, int k)
        else if (x == 0.25)
                y = 0.707106781186547524400844362104849039284835937688474036588339L;
        else
-               y = (k & 1) ? cos (M_PIgo * x) : sin (M_PIgo * x);
+               y = (k & 1) ? cosl (M_PIgo * x) : sinl (M_PIgo * x);
 
        return (k & 2) ? 0 - y : y;
 }