50 lines
1.0 KiB
C
50 lines
1.0 KiB
C
/*
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* This file is part of the UCB release of Plan 9. It is subject to the license
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* terms in the LICENSE file found in the top-level directory of this
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* distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
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* part of the UCB release of Plan 9, including this file, may be copied,
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* modified, propagated, or distributed except according to the terms contained
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* in the LICENSE file.
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*/
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/*
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* jehanne_asin(arg) and jehanne_acos(arg) return the arcsin, arccos,
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* respectively of their arguments.
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*
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* Arctan is called after appropriate range reduction.
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*/
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#include <u.h>
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#include <libc.h>
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double
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jehanne_asin(double arg)
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{
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double temp;
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int sign;
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sign = 0;
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if(arg < 0) {
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arg = -arg;
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sign++;
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}
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if(arg > 1)
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return jehanne_NaN();
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temp = jehanne_sqrt(1 - arg*arg);
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if(arg > 0.7)
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temp = PIO2 - jehanne_atan(temp/arg);
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else
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temp = jehanne_atan(arg/temp);
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if(sign)
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temp = -temp;
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return temp;
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}
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double
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jehanne_acos(double arg)
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{
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if(arg > 1 || arg < -1)
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return jehanne_NaN();
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return PIO2 - jehanne_asin(arg);
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}
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