From af59d142d62340859128cf604ded4bb3f052033d Mon Sep 17 00:00:00 2001
From: Oliver Sander <sander@igpm.rwth-aachen.de>
Date: Tue, 31 Aug 2010 13:07:59 +0000
Subject: [PATCH] simplify series expression of second derivative of arccos
squared
[[Imported from SVN: r6295]]
---
dune/gfe/unitvector.hh | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/dune/gfe/unitvector.hh b/dune/gfe/unitvector.hh
index 3283955f..f25332f6 100644
--- a/dune/gfe/unitvector.hh
+++ b/dune/gfe/unitvector.hh
@@ -27,7 +27,7 @@ class UnitVector
static double secondDerivativeOfArcCosSquared(const double& x) {
const double eps = 1e-12;
if (x > 1-eps) { // regular expression is unstable, use the series expansion instead
- return 1.0/6 - 17*(x-1)/60 + 1.0/2 - (x-1)/4;
+ return 2.0/3 - 8*(x-1)/15;
} else if (x < -1+eps) { // The function is not differentiable
DUNE_THROW(Dune::Exception, "arccos^2 is not differentiable at x==-1!");
} else
--
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