26 Numerics library [numerics]

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

26.8.6 Mathematical special functions [sf.cmath]

26.8.6.4 Complete elliptic integral of the first kind [sf.cmath.comp.ellint.1]

double comp_ellint_1(double k); float comp_ellint_1f(float k); long double comp_ellint_1l(long double k);
Effects: These functions compute the complete elliptic integral of the first kind of their respective arguments k.
Returns:
where k is k.