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/*
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 * asin(arg) and 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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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 NaN();
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	temp = sqrt(1 - arg*arg);
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	if(arg > 0.7)
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		temp = PIO2 - atan(temp/arg);
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	else
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		temp = 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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acos(double arg)
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{
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	if(arg > 1 || arg < -1)
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		return NaN();
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	return PIO2 - asin(arg);
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}