⑩天掌 Teaching Plan on Advanced Mathematics 数量积的坐标表达式 ia=a i+a,j+a, k, b=b,i+b,j+b, k db=(ai +a,j+a, k). (b, i +b,j+b, k) i与jk,∵t·=jk=k·L=0, i闩jk=1, ii=jj=k·k=1. i·b=a.b.+a.b.+a.b x XTianjin Polytechnic University Teaching Plan on Advanced Mathematics 数量积的坐标表达式 a  b =   (a i a j a k) x y z    + + (b i b j b k) x y z     + + i j k,     ⊥ ⊥ i  j = j  k = k  i = 0,       | i |=| j |=| k |= 1,     i  i = j  j = k  k = 1.       x x y y z z a  b = a b + a b + a b   a a i a j a k, x y z     = + + b bx i by j bzk     设 = + +