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#include <u.h>
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#include <libc.h>
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/*
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	tanh(arg) computes the hyperbolic tangent of its floating
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	point argument.
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	sinh and cosh are called except for large arguments, which
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	would cause overflow improperly.
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 */
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double
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tanh(double arg)
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{
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	if(arg < 0) {
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		arg = -arg;
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		if(arg > 21)
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			return -1;
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		return -sinh(arg)/cosh(arg);
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	}
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	if(arg > 21)
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		return 1;
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	return sinh(arg)/cosh(arg);
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}