Hence, the given two lines are
coplanar Example 30 Find the coordinates of the point where the line through the points
A (3, 4, 1) and B(5, 1, 6) crosses the XY-plane Solution The vector equation of the line through the points A and B is
 rr  =
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
3
4
[ (5
3)
(1
4)
(6
1)
]
i
j
k
i
j
k
+
+
+ λ
−
+
−
+
−
i e