Sigmoid 함수 (logistic function) sigmoid(x)=11+e−x sigmoid(x)=11+e−x Sigmoid 함수 미분 ddxsigmoid(x)=ddx(1+e−x)−1 ddxsigmoid(x)=ddx(1+e−x)−1 =(−1)1(1+e−x)2ddx(1+e−x) =(−1)1(1+e−x)2ddx(1+e−x) =(−1)1(1+e−x)2(0+e−x)ddx(−x) =(−1)1(1+e−x)2(0+e−x)ddx(−x) =(−1)1(1+e−x)2e−x(−1) =(−1)1(1+e−x)2e−x(−1) =(−1)1(1+e−x)2e−x(−1) =(−1)1(1+e−x)2e−x(−1) =(−1)1(1+e−x)2e−x(−1) =(−1)1(1+e−x)2e−x(−1) =(1+e−x)(1+e−x)2−1(1+e−..