// atan(x) at 21 points from x = -3.0 to x = 3.0
// cbrt(x) at 21 points from x = 0.0 to x = 1.0
// cos(x) at 21 points from x = -1.0 to x = 3.0
// cosh(x) at 21 points from x = 0.0 to x = 2.0
// erf(x) at 21 points from x = 0.0 to x = 2.0
// exp(x) at 21 points from x = -0.5 to x = 2.0
// lgamma(x) at 21 points from x = 0.1 to x = 1.0
// log(x) at 21 points from x = 0.1 to x = 1.0
// sin(x) at 21 points from x = -1.0 to x = 3.0
// tanh(x) at 21 points from x = 1.0 to x = 3.0