29.9 Mathematical functions for floating-point types [c.math]
double legendre(unsigned l, double x);
float legendref(unsigned l, float x);
long double legendrel(unsigned l, long double x);
Effects:
These functions compute the Legendre polynomials of their
respective arguments
l and x.
Returns:
Pℓ(x)=12ℓℓ!dℓdxℓ(x2−1)ℓ,for |x|≤1
where
l is l and
x is x.
Remarks:
The effect of calling each of these functions
is implementation-defined
if l >= 128.