Original formula =4 ∫ (upper limit π/4, lower limit 0) (1/(2π))dθ? ∫ (+∞, lower limit 0) E (-R 2/2) RDR

=(2/π) *? ∫ (upper limit π/4, lower limit 0) dθ *? ∫ (+∞, lower limit 0) E (-R 2/2) RDR

=(2/π) * (π/4) * 1

= 1/2