Source of image:http://www.offconvex.org/2016/03/22/saddlepoints/ Hessian L()around =0'can be approximated below L(0)*1(9)+00☑叶60-9H6-0y At critical point telling the properties of critical points local min local max saddle point 4 2 0 0 0 -2-2 -2-2 -2 Hessian Source of image:http://www.offconvex.org/2016/03/22/saddlepoints/ telling the properties of critical points 𝐿 𝜽 ≈ 𝐿 𝜽 ′ + 𝜽 − 𝜽 ′ 𝑇𝒈 + 1 2 𝜽 − 𝜽 ′ 𝑇𝐻 𝜽 − 𝜽 ′ 𝐿 𝜽 around 𝜽 = 𝜽 ′ can be approximated below At critical point