[code]
zeta21 = .2;
p1 = 20
alpha = 4
pc_e22 _ 2[b_] = Integrate[
(1 + b*y^(alpha)*p1*
Sqrt[x^2 + y^2 - 2*x*y*Cos (thab)]^(-alpha))^(-1), {x, (-1 +
zeta21^(-1))*y, (1 + zeta21^(-1))*y}, {y, 0, Infinity}, {thab,
0, 2*Pi}]
pc_e22 _ 2[2^(.2/100) - 1]
[/code]