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📄 abs.go(363 B)
📄 acos_s390x.s(3.73 KB)
📄 acosh.go(1.71 KB)
📄 acosh_s390x.s(4.32 KB)
📄 all_test.go(85.27 KB)
📄 arith_s390x.go(3.73 KB)
📄 arith_s390x_test.go(10.78 KB)
📄 asin.go(1.08 KB)
📄 asin_s390x.s(4.16 KB)
📄 asinh.go(1.92 KB)
📄 asinh_s390x.s(5.74 KB)
📄 atan.go(3.03 KB)
📄 atan2.go(1.52 KB)
📄 atan2_s390x.s(6.93 KB)
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📄 atanh.go(1.99 KB)
📄 atanh_s390x.s(5.36 KB)
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📁 bits
📄 bits.go(1.87 KB)
📄 cbrt.go(2.31 KB)
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📄 const.go(2.33 KB)
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📄 copysign.go(378 B)
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📄 erf.go(11.5 KB)
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📄 erfinv.go(3.36 KB)
📄 example_test.go(3.66 KB)
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📄 expm1.go(7.9 KB)
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📄 export_s390x_test.go(732 B)
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📄 floor.go(3.28 KB)
📄 floor_386.s(1.47 KB)
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📄 fma.go(4.46 KB)
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📄 gamma.go(5.52 KB)
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📄 hypot_386.s(1.81 KB)
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📄 lgamma.go(11.02 KB)
📄 log.go(3.86 KB)
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📁 rand
📄 remainder.go(2.04 KB)
📄 signbit.go(302 B)
📄 sin.go(6.35 KB)
📄 sin_s390x.s(8.34 KB)
📄 sincos.go(1.75 KB)
📄 sinh.go(1.69 KB)
📄 sinh_s390x.s(5.98 KB)
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📄 stubs.go(2.59 KB)
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📄 tan.go(3.67 KB)
📄 tan_s390x.s(2.73 KB)
📄 tanh.go(2.65 KB)
📄 tanh_s390x.s(4.57 KB)
📄 trig_reduce.go(3.33 KB)
📄 unsafe.go(1.27 KB)

Editing: tan.go

// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package math

/*
	Floating-point tangent.
*/

// The original C code, the long comment, and the constants
// below were from http://netlib.sandia.gov/cephes/cmath/sin.c,
// available from http://www.netlib.org/cephes/cmath.tgz.
// The go code is a simplified version of the original C.
//
//      tan.c
//
//      Circular tangent
//
// SYNOPSIS:
//
// double x, y, tan();
// y = tan( x );
//
// DESCRIPTION:
//
// Returns the circular tangent of the radian argument x.
//
// Range reduction is modulo pi/4.  A rational function
//       x + x**3 P(x**2)/Q(x**2)
// is employed in the basic interval [0, pi/4].
//
// ACCURACY:
//                      Relative error:
// arithmetic   domain     # trials      peak         rms
//    DEC      +-1.07e9      44000      4.1e-17     1.0e-17
//    IEEE     +-1.07e9      30000      2.9e-16     8.1e-17
//
// Partial loss of accuracy begins to occur at x = 2**30 = 1.074e9.  The loss
// is not gradual, but jumps suddenly to about 1 part in 10e7.  Results may
// be meaningless for x > 2**49 = 5.6e14.
// [Accuracy loss statement from sin.go comments.]
//
// Cephes Math Library Release 2.8:  June, 2000
// Copyright 1984, 1987, 1989, 1992, 2000 by Stephen L. Moshier
//
// The readme file at http://netlib.sandia.gov/cephes/ says:
//    Some software in this archive may be from the book _Methods and
// Programs for Mathematical Functions_ (Prentice-Hall or Simon & Schuster
// International, 1989) or from the Cephes Mathematical Library, a
// commercial product. In either event, it is copyrighted by the author.
// What you see here may be used freely but it comes with no support or
// guarantee.
//
//   The two known misprints in the book are repaired here in the
// source listings for the gamma function and the incomplete beta
// integral.
//
//   Stephen L. Moshier
//   moshier@na-net.ornl.gov

// tan coefficients
var _tanP = [...]float64{
	-1.30936939181383777646e4, // 0xc0c992d8d24f3f38
	1.15351664838587416140e6,  // 0x413199eca5fc9ddd
	-1.79565251976484877988e7, // 0xc1711fead3299176
}
var _tanQ = [...]float64{
	1.00000000000000000000e0,
	1.36812963470692954678e4,  //0x40cab8a5eeb36572
	-1.32089234440210967447e6, //0xc13427bc582abc96
	2.50083801823357915839e7,  //0x4177d98fc2ead8ef
	-5.38695755929454629881e7, //0xc189afe03cbe5a31
}

// Tan returns the tangent of the radian argument x.
//
// Special cases are:
//	Tan(±0) = ±0
//	Tan(±Inf) = NaN
//	Tan(NaN) = NaN
func Tan(x float64) float64 {
	if haveArchTan {
		return archTan(x)
	}
	return tan(x)
}

func tan(x float64) float64 {
	const (
		PI4A = 7.85398125648498535156e-1  // 0x3fe921fb40000000, Pi/4 split into three parts
		PI4B = 3.77489470793079817668e-8  // 0x3e64442d00000000,
		PI4C = 2.69515142907905952645e-15 // 0x3ce8469898cc5170,
	)
	// special cases
	switch {
	case x == 0 || IsNaN(x):
		return x // return ±0 || NaN()
	case IsInf(x, 0):
		return NaN()
	}

// make argument positive but save the sign
	sign := false
	if x < 0 {
		x = -x
		sign = true
	}
	var j uint64
	var y, z float64
	if x >= reduceThreshold {
		j, z = trigReduce(x)
	} else {
		j = uint64(x * (4 / Pi)) // integer part of x/(Pi/4), as integer for tests on the phase angle
		y = float64(j)           // integer part of x/(Pi/4), as float

/* map zeros and singularities to origin */
		if j&1 == 1 {
			j++
			y++
		}

z = ((x - y*PI4A) - y*PI4B) - y*PI4C
	}
	zz := z * z

if zz > 1e-14 {
		y = z + z*(zz*(((_tanP[0]*zz)+_tanP[1])*zz+_tanP[2])/((((zz+_tanQ[1])*zz+_tanQ[2])*zz+_tanQ[3])*zz+_tanQ[4]))
	} else {
		y = z
	}
	if j&2 == 2 {
		y = -1 / y
	}
	if sign {
		y = -y
	}
	return y
}

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Editing: tan.go

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