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1 | /* @(#)s_tan.c 5.1 93/09/24 */\r |
| 2 | /*\r |
| 3 | * ====================================================\r |
| 4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.\r |
| 5 | *\r |
| 6 | * Developed at SunPro, a Sun Microsystems, Inc. business.\r |
| 7 | * Permission to use, copy, modify, and distribute this\r |
| 8 | * software is freely granted, provided that this notice\r |
| 9 | * is preserved.\r |
| 10 | * ====================================================\r |
| 11 | */\r |
| 12 | #include <LibConfig.h>\r |
| 13 | #include <sys/EfiCdefs.h>\r |
| 14 | #if defined(LIBM_SCCS) && !defined(lint)\r |
| 15 | __RCSID("$NetBSD: s_tan.c,v 1.10 2002/05/26 22:01:58 wiz Exp $");\r |
| 16 | #endif\r |
| 17 | \r |
| 18 | /* tan(x)\r |
| 19 | * Return tangent function of x.\r |
| 20 | *\r |
| 21 | * kernel function:\r |
| 22 | * __kernel_tan ... tangent function on [-pi/4,pi/4]\r |
| 23 | * __ieee754_rem_pio2 ... argument reduction routine\r |
| 24 | *\r |
| 25 | * Method.\r |
| 26 | * Let S,C and T denote the sin, cos and tan respectively on\r |
| 27 | * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2\r |
| 28 | * in [-pi/4 , +pi/4], and let n = k mod 4.\r |
| 29 | * We have\r |
| 30 | *\r |
| 31 | * n sin(x) cos(x) tan(x)\r |
| 32 | * ----------------------------------------------------------\r |
| 33 | * 0 S C T\r |
| 34 | * 1 C -S -1/T\r |
| 35 | * 2 -S -C T\r |
| 36 | * 3 -C S -1/T\r |
| 37 | * ----------------------------------------------------------\r |
| 38 | *\r |
| 39 | * Special cases:\r |
| 40 | * Let trig be any of sin, cos, or tan.\r |
| 41 | * trig(+-INF) is NaN, with signals;\r |
| 42 | * trig(NaN) is that NaN;\r |
| 43 | *\r |
| 44 | * Accuracy:\r |
| 45 | * TRIG(x) returns trig(x) nearly rounded\r |
| 46 | */\r |
| 47 | \r |
| 48 | #include "math.h"\r |
| 49 | #include "math_private.h"\r |
| 50 | \r |
| 51 | double\r |
| 52 | tan(double x)\r |
| 53 | {\r |
| 54 | double y[2],z=0.0;\r |
| 55 | int32_t n, ix;\r |
| 56 | \r |
| 57 | /* High word of x. */\r |
| 58 | GET_HIGH_WORD(ix,x);\r |
| 59 | \r |
| 60 | /* |x| ~< pi/4 */\r |
| 61 | ix &= 0x7fffffff;\r |
| 62 | if(ix <= 0x3fe921fb) return __kernel_tan(x,z,1);\r |
| 63 | \r |
| 64 | /* tan(Inf or NaN) is NaN */\r |
| 65 | else if (ix>=0x7ff00000) return x-x; /* NaN */\r |
| 66 | \r |
| 67 | /* argument reduction needed */\r |
| 68 | else {\r |
| 69 | n = __ieee754_rem_pio2(x,y);\r |
| 70 | return __kernel_tan(y[0],y[1],1-((n&1)<<1)); /* 1 -- n even\r |
| 71 | -1 -- n odd */\r |
| 72 | }\r |
| 73 | }\r |
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