2.1.2.矩阵乘法 设A∈Rmxm,B∈RmxP, C=AB∈RmxP, where Cy=∑aabg k=1 给定x,y∈R,x'y称为内积(inner product or dot product), xyeR=∑x i1 ·给定x∈Rm,y∈R,xyI称为外积(outer product), XIV1 xy2· X1yn X2y1X2y2·· XyT∈Rmx"= X2yn Xm1Xm2· Xmyn 6/812.1.2. 矩阵乘法 ▶ 设 A ∈ R m×n , B ∈ R n×p , C = AB ∈ R m×p , where Cij = Xn k=1 aikbkj ▶ 给定 x, y ∈ R n , x Ty 称为内积(inner product or dot product), x T y ∈ R = Xn i=1 xiyi . ▶ 给定 x ∈ R m , y ∈ R n , xyT 称为外积(outer product). xyT ∈ R m×n =      x1y1 x1y2 · · · x1yn x2y1 x2y2 · · · x2yn . . . . . . . . . . . . xmy1 xmy2 · · · xmyn      6 / 81