Question

向量代数概念和坐标,求详解

Answer 1

(7)

a的始点坐标=(x,y,z)

(2,-1,7) -(x,y,z) = (4,-4,7)

(x,y,z) = (-2,3,0)

(8)

α=60°

β=120°

γ= ?

(cosα)^2 +(cosβ)^2+(cosγ)^2= 1

(cosγ)^2 =1/2

cosγ=√2/2 or - √2/2

γ = 45° or 135°