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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/float/tanf.c
parent22358dd7ce7bb49792204b698f01a6f69b9c8e08 (diff)
uClibc now has a math library. muahahahaha!
-Erik
Diffstat (limited to 'libm/float/tanf.c')
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1 files changed, 192 insertions, 0 deletions
diff --git a/libm/float/tanf.c b/libm/float/tanf.c
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+/* tanf.c
+ *
+ * Circular tangent
+ *
+ *
+ *
+ * SYNOPSIS:
+ *
+ * float x, y, tanf();
+ *
+ * y = tanf( x );
+ *
+ *
+ *
+ * DESCRIPTION:
+ *
+ * Returns the circular tangent of the radian argument x.
+ *
+ * Range reduction is modulo pi/4. A polynomial approximation
+ * is employed in the basic interval [0, pi/4].
+ *
+ *
+ *
+ * ACCURACY:
+ *
+ * Relative error:
+ * arithmetic domain # trials peak rms
+ * IEEE +-4096 100000 3.3e-7 4.5e-8
+ *
+ * ERROR MESSAGES:
+ *
+ * message condition value returned
+ * tanf total loss x > 2^24 0.0
+ *
+ */
+ /* cotf.c
+ *
+ * Circular cotangent
+ *
+ *
+ *
+ * SYNOPSIS:
+ *
+ * float x, y, cotf();
+ *
+ * y = cotf( x );
+ *
+ *
+ *
+ * DESCRIPTION:
+ *
+ * Returns the circular cotangent of the radian argument x.
+ * A common routine computes either the tangent or cotangent.
+ *
+ *
+ *
+ * ACCURACY:
+ *
+ * Relative error:
+ * arithmetic domain # trials peak rms
+ * IEEE +-4096 100000 3.0e-7 4.5e-8
+ *
+ *
+ * ERROR MESSAGES:
+ *
+ * message condition value returned
+ * cot total loss x > 2^24 0.0
+ * cot singularity x = 0 MAXNUMF
+ *
+ */
+
+/*
+Cephes Math Library Release 2.2: June, 1992
+Copyright 1984, 1987, 1989 by Stephen L. Moshier
+Direct inquiries to 30 Frost Street, Cambridge, MA 02140
+*/
+
+/* Single precision circular tangent
+ * test interval: [-pi/4, +pi/4]
+ * trials: 10000
+ * peak relative error: 8.7e-8
+ * rms relative error: 2.8e-8
+ */
+#include <math.h>
+
+extern float MAXNUMF;
+
+static float DP1 = 0.78515625;
+static float DP2 = 2.4187564849853515625e-4;
+static float DP3 = 3.77489497744594108e-8;
+float FOPI = 1.27323954473516; /* 4/pi */
+static float lossth = 8192.;
+/*static float T24M1 = 16777215.;*/
+
+
+static float tancotf( float xx, int cotflg )
+{
+float x, y, z, zz;
+long j;
+int sign;
+
+
+/* make argument positive but save the sign */
+if( xx < 0.0 )
+ {
+ x = -xx;
+ sign = -1;
+ }
+else
+ {
+ x = xx;
+ sign = 1;
+ }
+
+if( x > lossth )
+ {
+ if( cotflg )
+ mtherr( "cotf", TLOSS );
+ else
+ mtherr( "tanf", TLOSS );
+ return(0.0);
+ }
+
+/* compute x mod PIO4 */
+j = FOPI * x; /* integer part of x/(PI/4) */
+y = j;
+
+/* map zeros and singularities to origin */
+if( j & 1 )
+ {
+ j += 1;
+ y += 1.0;
+ }
+
+z = ((x - y * DP1) - y * DP2) - y * DP3;
+
+zz = z * z;
+
+if( x > 1.0e-4 )
+ {
+/* 1.7e-8 relative error in [-pi/4, +pi/4] */
+ y =
+ ((((( 9.38540185543E-3 * zz
+ + 3.11992232697E-3) * zz
+ + 2.44301354525E-2) * zz
+ + 5.34112807005E-2) * zz
+ + 1.33387994085E-1) * zz
+ + 3.33331568548E-1) * zz * z
+ + z;
+ }
+else
+ {
+ y = z;
+ }
+
+if( j & 2 )
+ {
+ if( cotflg )
+ y = -y;
+ else
+ y = -1.0/y;
+ }
+else
+ {
+ if( cotflg )
+ y = 1.0/y;
+ }
+
+if( sign < 0 )
+ y = -y;
+
+return( y );
+}
+
+
+float tanf( float x )
+{
+
+return( tancotf(x,0) );
+}
+
+float cotf( float x )
+{
+
+if( x == 0.0 )
+ {
+ mtherr( "cotf", SING );
+ return( MAXNUMF );
+ }
+return( tancotf(x,1) );
+}
+