Elliptic complete elliptic integral of the second kind (SymPy, WMA)
EllipticE
[m]EllipticE
[$\phi$|m]Elliptic curves give Pi / 2 when evaluated at zero:
EllipticE[0]
EllipticE[0.3, 0.8]
Plot over a reals centered around 0:
Plot[EllipticE[m], {m, -2, 2}]