= j=1 N −1 In → ∞, it is equivalent to GP , ′ = ′ = −1 −1 = 2 (−1 , ′ , −1 , ′ , −1 , ′ ) = 1 2 −1 , −1 ′, ′ sin ,′ −1 + − ,′ −1 cos ,′ −1 ,′ = cos−1 ′, ′ −1 , −1 ′, ′ [Cho & Saul. 2009] When is ReLU It is very difficult to get analytical formula because of CLT