Function: ellK
Section: transcendental
C-Name: ellK
Prototype: Gp
Help: ellK(k): Complete elliptic integral of the first kind for the
 complex parameter k using the agm.
Doc: Complete elliptic integral of the first kind
 $$K(k)=\int_{0}^{\pi/2}(1-k^{2}\sin(t)^{2})^{-1/2}\,dt$$ for the
 complex parameter $k$ using the agm.
