28 Numerics library [numerics]

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

28.7.6 Mathematical special functions [sf.cmath] Incomplete elliptic integral of the first kind [sf.cmath.ellint.1]

floating-point-type ellint_1(floating-point-type k, floating-point-type phi); float ellint_1f(float k, float phi); long double ellint_1l(long double k, long double phi);
Effects: These functions compute the incomplete elliptic integral of the first kind of their respective arguments k and phi (phi measured in radians).
where k is k and φ is phi.