The coordinates of the mid-points are D(1,5,−1),E(0,4,−2),F(2,3,4)
The relation between the coordinates of vertex of triangle and the mid points is
x1+x2
2
=1,
y1+y2
2
=5,
z1+z2
2
=−1 x1+x2=2,y1+y2=10,z1+z2=−2 For other two sides, x2+x3=0,y2+y3=8,z2+z3=−4 x1+x3=4,y1+y3=6,z1+z3=8 By using the above relations 2(x1+x2+x3)=6 2(y1+y2+y3)=24 2(z1+z2+z3)=2 x3=1,y3=2,z3=3 The length of the median CD is CD=√(1−1)2+(2−5)2+(−1−3)2=5