3 * Circular sine and cosine of argument in degrees
4 * Table lookup and interpolation algorithm
10 * double x, sine, cosine, flg, sincos();
12 * sincos( x, &sine, &cosine, flg );
18 * Returns both the sine and the cosine of the argument x.
19 * Several different compile time options and minimax
20 * approximations are supplied to permit tailoring the
21 * tradeoff between computation speed and accuracy.
23 * Since range reduction is time consuming, the reduction
24 * of x modulo 360 degrees is also made optional.
26 * sin(i) is internally tabulated for 0 <= i <= 90 degrees.
27 * Approximation polynomials, ranging from linear interpolation
28 * to cubics in (x-i)**2, compute the sine and cosine
29 * of the residual x-i which is between -0.5 and +0.5 degree.
30 * In the case of the high accuracy options, the residual
31 * and the tabulated values are combined using the trigonometry
32 * formulas for sin(A+B) and cos(A+B).
34 * Compile time options are supplied for 5, 11, or 17 decimal
35 * relative accuracy (ACC5, ACC11, ACC17 respectively).
36 * A subroutine flag argument "flg" chooses betwen this
37 * accuracy and table lookup only (peak absolute error
40 * If the argument flg = 1, then the tabulated value is
41 * returned for the nearest whole number of degrees. The
42 * approximation polynomials are not computed. At
43 * x = 0.5 deg, the absolute error is then sin(0.5) = 0.0087.
45 * An intermediate speed and precision can be obtained using
46 * the compile time option LINTERP and flg = 1. This yields
47 * a linear interpolation using a slope estimated from the sine
48 * or cosine at the nearest integer argument. The peak absolute
49 * error with this option is 3.8e-5. Relative error at small
50 * angles is about 1e-5.
52 * If flg = 0, then the approximation polynomials are computed
59 * Relative speed comparisons follow for 6MHz IBM AT clone
60 * and Microsoft C version 4.0. These figures include
61 * software overhead of do loop and function calls.
62 * Since system hardware and software vary widely, the
63 * numbers should be taken as representative only.
65 * flg=0 flg=0 flg=1 flg=1
66 * ACC11 ACC5 LINTERP Lookup only
68 * sin(), cos() 1.0 1.0 1.0 1.0
71 * sincos() 1.1 1.4 1.9 3.0
74 * sin(), cos() 0.19 0.19 0.19 0.19
77 * sincos() 0.39 0.50 0.73 1.7
83 * The accurate approximations are designed with a relative error
84 * criterion. The absolute error is greatest at x = 0.5 degree.
85 * It decreases from a local maximum at i+0.5 degrees to full
86 * machine precision at each integer i degrees. With the
87 * ACC5 option, the relative error of 6.3e-6 is equivalent to
88 * an absolute angular error of 0.01 arc second in the argument
89 * at x = i+0.5 degrees. For small angles < 0.5 deg, the ACC5
90 * accuracy is 6.3e-6 (.00063%) of reading; i.e., the absolute
91 * error decreases in proportion to the argument. This is true
92 * for both the sine and cosine approximations, since the latter
93 * is for the function 1 - cos(x).
95 * If absolute error is of most concern, use the compile time
96 * option ABSERR to obtain an absolute error of 2.7e-8 for ACC5
97 * precision. This is about half the absolute error of the
98 * relative precision option. In this case the relative error
99 * for small angles will increase to 9.5e-6 -- a reasonable
106 /* Define one of the following to be 1:
112 /* Option for linear interpolation when flg = 1
116 /* Option for absolute error criterion
120 /* Option to include modulo 360 function:
125 Cephes Math Library Release 2.1
126 Copyright 1987 by Stephen L. Moshier
127 Direct inquiries to 30 Frost Street, Cambridge, MA 02140
131 /* Table of sin(i degrees)
134 static double sintbl[92] = {
135 0.00000000000000000000E0,
136 1.74524064372835128194E-2,
137 3.48994967025009716460E-2,
138 5.23359562429438327221E-2,
139 6.97564737441253007760E-2,
140 8.71557427476581735581E-2,
141 1.04528463267653471400E-1,
142 1.21869343405147481113E-1,
143 1.39173100960065444112E-1,
144 1.56434465040230869010E-1,
145 1.73648177666930348852E-1,
146 1.90808995376544812405E-1,
147 2.07911690817759337102E-1,
148 2.24951054343864998051E-1,
149 2.41921895599667722560E-1,
150 2.58819045102520762349E-1,
151 2.75637355816999185650E-1,
152 2.92371704722736728097E-1,
153 3.09016994374947424102E-1,
154 3.25568154457156668714E-1,
155 3.42020143325668733044E-1,
156 3.58367949545300273484E-1,
157 3.74606593415912035415E-1,
158 3.90731128489273755062E-1,
159 4.06736643075800207754E-1,
160 4.22618261740699436187E-1,
161 4.38371146789077417453E-1,
162 4.53990499739546791560E-1,
163 4.69471562785890775959E-1,
164 4.84809620246337029075E-1,
165 5.00000000000000000000E-1,
166 5.15038074910054210082E-1,
167 5.29919264233204954047E-1,
168 5.44639035015027082224E-1,
169 5.59192903470746830160E-1,
170 5.73576436351046096108E-1,
171 5.87785252292473129169E-1,
172 6.01815023152048279918E-1,
173 6.15661475325658279669E-1,
174 6.29320391049837452706E-1,
175 6.42787609686539326323E-1,
176 6.56059028990507284782E-1,
177 6.69130606358858213826E-1,
178 6.81998360062498500442E-1,
179 6.94658370458997286656E-1,
180 7.07106781186547524401E-1,
181 7.19339800338651139356E-1,
182 7.31353701619170483288E-1,
183 7.43144825477394235015E-1,
184 7.54709580222771997943E-1,
185 7.66044443118978035202E-1,
186 7.77145961456970879980E-1,
187 7.88010753606721956694E-1,
188 7.98635510047292846284E-1,
189 8.09016994374947424102E-1,
190 8.19152044288991789684E-1,
191 8.29037572555041692006E-1,
192 8.38670567945424029638E-1,
193 8.48048096156425970386E-1,
194 8.57167300702112287465E-1,
195 8.66025403784438646764E-1,
196 8.74619707139395800285E-1,
197 8.82947592858926942032E-1,
198 8.91006524188367862360E-1,
199 8.98794046299166992782E-1,
200 9.06307787036649963243E-1,
201 9.13545457642600895502E-1,
202 9.20504853452440327397E-1,
203 9.27183854566787400806E-1,
204 9.33580426497201748990E-1,
205 9.39692620785908384054E-1,
206 9.45518575599316810348E-1,
207 9.51056516295153572116E-1,
208 9.56304755963035481339E-1,
209 9.61261695938318861916E-1,
210 9.65925826289068286750E-1,
211 9.70295726275996472306E-1,
212 9.74370064785235228540E-1,
213 9.78147600733805637929E-1,
214 9.81627183447663953497E-1,
215 9.84807753012208059367E-1,
216 9.87688340595137726190E-1,
217 9.90268068741570315084E-1,
218 9.92546151641322034980E-1,
219 9.94521895368273336923E-1,
220 9.96194698091745532295E-1,
221 9.97564050259824247613E-1,
222 9.98629534754573873784E-1,
223 9.99390827019095730006E-1,
224 9.99847695156391239157E-1,
225 1.00000000000000000000E0,
226 9.99847695156391239157E-1,
230 double floor ( double );
235 int sincos(x, s, c, flg)
240 int ix, ssign, csign, xsign;
241 double y, z, sx, sz, cx, cz;
243 /* Make argument nonnegative.
254 x = x - 360.0 * floor( x/360.0 );
257 /* Find nearest integer to x.
258 * Note there should be a domain error test here,
259 * but this is omitted to gain speed.
262 z = x - ix; /* the residual */
264 /* Look up the sine and cosine of the integer.
287 cx = sintbl[ 90-ix ];
291 /* If the flag argument is set, then just return
292 * the tabulated values for arg to the nearest whole degree.
297 y = sx + 1.74531263774940077459e-2 * z * cx;
298 cx -= 1.74531263774940077459e-2 * z * sx;
304 *c = cx; /* cosine */
314 /* Find sine and cosine
315 * of the residual angle between -0.5 and +0.5 degree.
319 /* absolute error = 2.769e-8: */
320 sz = 1.74531263774940077459e-2 * z;
321 /* absolute error = 4.146e-11: */
322 cz = 1.0 - 1.52307909153324666207e-4 * z * z;
324 /* relative error = 6.346e-6: */
325 sz = 1.74531817576426662296e-2 * z;
326 /* relative error = 3.173e-6: */
327 cz = 1.0 - 1.52308226602566149927e-4 * z * z;
335 sz = ( -8.86092781698004819918e-7 * y
336 + 1.74532925198378577601e-2 ) * z;
338 cz = 1.0 - ( -3.86631403698859047896e-9 * y
339 + 1.52308709893047593702e-4 ) * y;
344 sz = (( 1.34959795251974073996e-11 * y
345 - 8.86096155697856783296e-7 ) * y
346 + 1.74532925199432957214e-2 ) * z;
348 cz = 1.0 - (( 3.92582397764340914444e-14 * y
349 - 3.86632385155548605680e-9 ) * y
350 + 1.52308709893354299569e-4 ) * y;
354 /* Combine the tabulated part and the calculated part
357 y = sx * cz + cx * sz;
362 *c = cx * cz - sx * sz; /* cosine */