R-a⁡(b;z)=2B⁡(b1,b2)⁢∫0π/2(z1⁢cos2⁡θ+z2⁢sin2⁡θ)-a⁢(cos⁡θ)2⁢b1-1⁢(sin⁡θ)2⁢b2-1⁢ⅆ⁡θ,