q/|q|*n=|q|n*n/|q|^3=1/|q|^2=1/r^2
1/r^2dS=(1/r^2)r^2sintdsdt=-1costdtds=4π

p=(a,0,0)
q-p=an-(a,0,0)
(q-p)*n=an*n-(a,0,0)*(sintcoss,sintsins,cost)=a(1-sintcoss)
|q-p|^2=a^2(sintcoss-1,sintsins,cost)^2=2a^2(1-sintcoss)
(q-p)*n/|q-p|^3=(1-sintcoss)/(1-sintcoss)^3=1/(1-sintcoss)^2
(q-p)*n/|q-p|^3dS=1/(1-sintcoss)^2sintdtds