τ = ( -1+√-3 )/2 = ζ3

η( √-3 )

= 1/( 2^( 2/3 )A.G.M.( 1 , cos( π/12 ) )^( 1/2 ) )

= 0.635420293 ・・・

E4( Z[ √-3 ] )

= ( 15/16 )/A.G.M.( 1 , cos( π/12 ) )^4

= 1.0045076097 ・・・