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tanh
Hyperbolic tangent.SYNOPSIS:
double x, y, tanh();
y = tanh(x);
DESCRIPTION:
Returns the hyperbolic tangent of an argument in the range MINLOG to MAXLOG.
A rational function is used for |x| < 0.625. The form:
x + x**3 P(x)/Q(x) of Cody _& Waite
is employed.
Otherwise:
tanh(x) = sinh(x)/cosh(x) = 1 - 2/(exp(2x) + 1).
ACCURACY:
Relative error:
arithmetic domain # trials peak rms
DEC -2,2 50000 3.3e-17 6.4e-18
IEEE -2,2 30000 2.5e-16 5.8e-17