Given points C (2; 2; 2) D (-1; 1; 3) find the midpoints of the segment CD.

If the coordinates of the ends of any segment are respectively equal to (x1; y1; z1) and (x2; y2; z2), respectively, then the coordinates of its middle are calculated as the arithmetic mean of these coordinates, ((x1 + x2) / 2; (y1 + y2 ) / 2; (z1 + z2) / 2)

Let M be the midpoint of the segment CD.

Then X (M) = (Xc + Xd) / 2 = (2 – 1) / 2 = 1/2;

Y (M) = (Yc + Yd) / 2 = (2 + 1) / 2 = 3/2;

Z (M) = (Zc + Zd) / 2 = (2 + 3) / 2 = 5/2.

Answer. M (1/2; 3/2; 5/2).