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authorEric Andersen <andersen@codepoet.org>2001-05-10 00:40:28 +0000
committerEric Andersen <andersen@codepoet.org>2001-05-10 00:40:28 +0000
commit1077fa4d772832f77a677ce7fb7c2d513b959e3f (patch)
tree579bee13fb0b58d2800206366ec2caecbb15f3fc /libm/double/cosh.c
parent22358dd7ce7bb49792204b698f01a6f69b9c8e08 (diff)
uClibc now has a math library. muahahahaha!
-Erik
Diffstat (limited to 'libm/double/cosh.c')
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diff --git a/libm/double/cosh.c b/libm/double/cosh.c
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+/* cosh.c
+ *
+ * Hyperbolic cosine
+ *
+ *
+ *
+ * SYNOPSIS:
+ *
+ * double x, y, cosh();
+ *
+ * y = cosh( x );
+ *
+ *
+ *
+ * DESCRIPTION:
+ *
+ * Returns hyperbolic cosine of argument in the range MINLOG to
+ * MAXLOG.
+ *
+ * cosh(x) = ( exp(x) + exp(-x) )/2.
+ *
+ *
+ *
+ * ACCURACY:
+ *
+ * Relative error:
+ * arithmetic domain # trials peak rms
+ * DEC +- 88 50000 4.0e-17 7.7e-18
+ * IEEE +-MAXLOG 30000 2.6e-16 5.7e-17
+ *
+ *
+ * ERROR MESSAGES:
+ *
+ * message condition value returned
+ * cosh overflow |x| > MAXLOG MAXNUM
+ *
+ *
+ */
+
+/* cosh.c */
+
+/*
+Cephes Math Library Release 2.8: June, 2000
+Copyright 1985, 1995, 2000 by Stephen L. Moshier
+*/
+
+#include <math.h>
+#ifdef ANSIPROT
+extern double exp ( double );
+extern int isnan ( double );
+extern int isfinite ( double );
+#else
+double exp();
+int isnan(), isfinite();
+#endif
+extern double MAXLOG, INFINITY, LOGE2;
+
+double cosh(x)
+double x;
+{
+double y;
+
+#ifdef NANS
+if( isnan(x) )
+ return(x);
+#endif
+if( x < 0 )
+ x = -x;
+if( x > (MAXLOG + LOGE2) )
+ {
+ mtherr( "cosh", OVERFLOW );
+ return( INFINITY );
+ }
+if( x >= (MAXLOG - LOGE2) )
+ {
+ y = exp(0.5 * x);
+ y = (0.5 * y) * y;
+ return(y);
+ }
+y = exp(x);
+y = 0.5 * (y + 1.0 / y);
+return( y );
+}