江画工太猩院 ia=a i+aj+a, k, b=b, i+bj+b, k n,b=(a,1+a,j+4),+bj+b4) 7=jk=k·i=0. i曰jk=1, jj=k·k ·b=a.b.+a.b.+a.b 数量积的坐标表达式江西理工大学理学院 a a i a j a k, x y z r r r r = + + b b i b j b k x y z r r r r 设 = + + a ⋅ b = r r (a i a j a k) x y z r r r + + (b i b j b k) x y z r r r ⋅ + + i j k, r r r Q ⊥ ⊥ ∴i ⋅ j = j ⋅ k = k ⋅ i = 0, r r r r r r | i |=| j |=| k |= 1, r r r Q ∴i ⋅ i = j ⋅ j = k ⋅ k = 1. r r r r r r x x y y z z a ⋅ b = a b + a b + a b r r 数量积的坐标表达式