显然:MM2向量可以表示为:
(x2-x, y2-y, z2-z)
因为M1M=λMM2
而M1M2=M1M+MM2, 则有
向量M1M2 =(1+λ)向量MM2
而M1M2=(x2-x1, y2-y1, z2-z1)
则:
((1+λ)(x2-x),(1+λ)(y2-y),(1+λ)(z2-z))=(x2-x1, y2-y1, z2-z1)
对比可知:
(1+λ)(x2-x)=(x2-x1),
(1+λ)(y2-y)= (y2-y1),
(1+λ)(z2-z)=(z2-z1)
解得:
x=(x1+λx2)/(1+λ)
y=(y1+λy2)/(1+λ)
z=(z1+λz2)/(1+λ)