公式1: ∂∂X(XXT)=2X\frac{\partial }{\partial X}(XX^T) = 2X∂X∂(XXT)=2X 公式2: ∂∂θ(Xθ)=XT\frac{\partial }{\partial \theta}(X \theta) = X^T∂θ∂(Xθ)=XT