Let A ∈ R^(N×N) be a symmetric positive
definite matrix and b ∈ R^N a vector.
If x ∈ R^N , evaluate the integral
Z(A,b) = ∫e^(−(1/2)x^T Ax + b^T x) dx as a function
of A and b.
Let f(W) be a function of vector W ∈ R^N ,
i.e. f(W) = (1/(1 + e^(−W^T x) ))
Determine the first derivative and
matrix of second derivatives of f with
respect to W