double comp_ellint_2(double k);
float comp_ellint_2f(float k);
long double comp_ellint_2l(long double k);
Effects: These functions compute the complete elliptic integral of the second kind of their respective arguments k.
Returns: E(k) = E(k, π / 2), for |k| ≤ 1 where k is k.
See also [sf.cmath.ellint_2].