Let R and S be the two points of trisection:
Ratio at R is 1 : 2
∴ Point R is
Also, ratio at S is 2 : 1
∴ Point S is
Find the ratio in which the YZ-plane divides the line segment formed by joining the points (–2, 4, 7) and (3, –5, 8).
Find the ratio in which the join of P (2, 1, -1) and Q (3, 2, 4) is divided by XY-plane.