26 Numerics library [numerics]

26.8 Mathematical functions for floating-point types [c.math]

26.8.6 Mathematical special functions [sf.cmath] Spherical associated Legendre functions [sf.cmath.sph.legendre]

double sph_legendre(unsigned l, unsigned m, double theta); float sph_legendref(unsigned l, unsigned m, float theta); long double sph_legendrel(unsigned l, unsigned m, long double theta);
Effects: These functions compute the spherical associated Legendre functions of their respective arguments l, m, and theta (theta measured in radians).
and l is l, m is m, and ΞΈ is theta.
Remarks: The effect of calling each of these functions is implementation-defined if l >= 128.