| // Copyright 2009 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 |
| |
| export sin, cos |
| |
| const |
| ( |
| p0 = .1357884097877375669092680e8; |
| p1 = -.4942908100902844161158627e7; |
| p2 = .4401030535375266501944918e6; |
| p3 = -.1384727249982452873054457e5; |
| p4 = .1459688406665768722226959e3; |
| q0 = .8644558652922534429915149e7; |
| q1 = .4081792252343299749395779e6; |
| q2 = .9463096101538208180571257e4; |
| q3 = .1326534908786136358911494e3; |
| piu2 = .6366197723675813430755350e0; // 2/pi |
| ) |
| |
| func |
| sinus(arg float64, quad int) float64 |
| { |
| var e, f, ysq, x, y, temp1, temp2 float64; |
| var k long; |
| |
| x = arg; |
| if(x < 0) { |
| x = -x; |
| quad = quad+2; |
| } |
| x = x * piu2; /* underflow? */ |
| if x > 32764 { |
| e,y = sys.modf(x); |
| e = e + float64(quad); |
| temp1,f = sys.modf(0.25*e); |
| quad = int(e - 4*f); |
| } else { |
| k = long(x); |
| y = x - float64(k); |
| quad = (quad + int(k)) & 3; |
| } |
| |
| if quad&1 != 0 { |
| y = 1-y; |
| } |
| if quad > 1 { |
| y = -y; |
| } |
| |
| ysq = y*y; |
| temp1 = ((((p4*ysq+p3)*ysq+p2)*ysq+p1)*ysq+p0)*y; |
| temp2 = ((((ysq+q3)*ysq+q2)*ysq+q1)*ysq+q0); |
| return temp1/temp2; |
| } |
| |
| func |
| cos(arg float64) float64 |
| { |
| if arg < 0 { |
| arg = -arg; |
| } |
| return sinus(arg, 1); |
| } |
| |
| func |
| sin(arg float64) float64 |
| { |
| return sinus(arg, 0); |
| } |