吳恩達深度學習 —— 3.10 直觀理解反向傳播

z [ 1 ] = W [ 1 ] x + b [ 1 ] z^{[1]}=W^{[1]}x+b^{[1]} z[1]=W[1]x+b[1] a [ 1 ] = σ ( z [ 1 ] ) a^{[1]}=\sigma(z^{[1]}) a[1]=σ(z[1]) z [ 2 ] = W a [ 1 ] [ 2 ] + b [ 2 ] z^{[2]}=W^{[2]}_{a^{[1]}}+b^{[2]

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