@acer  

what i meant  that if a:=0.6364562590  its approximatly a:=0.64 how i evaluate this approximation by maple

@Carl Love thanks alot sir it actually doesnt work in 3d plot 

@vv excuse me sir but could you explain more what did you mean  by the inner sum and outer sum 
(thanks alot for your help)

@Carl Love actually sir it does work when i replease infinity with 100 but does it mathematically true

@Carl Love