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cosdg
Circular cosine of angle in degrees.SYNOPSIS:
double x, y, cosdg();
y = cosdg(x);
DESCRIPTION:
Range reduction is into intervals of 45 degrees. Two polynomial approximating functions are employed.
Between 0 and pi/4 the cosine is approximated by:
1 - x**2 P(x**2).
Between pi/4 and pi/2 the sine is represented as:
x + x**3 P(x**2).
ACCURACY:
Relative error:
arithmetic domain # trials peak rms
DEC +-1000 3400 3.5e-17 9.1e-18
IEEE +-1000 30000 2.1e-16 5.7e-17