Joining the points P1 and P2 with the origin
O, and applying triangle law, from the triangle
OP1P2, we have
1
1 2
OP
uuur+P P
uuuur  =
OP 2
uuuur
Using the properties of vector addition, the
above equation becomes
1 2
P P
uuuur  =
2
1
OP
OP
−
uuuur
uuur
i e 1 2
P P
uuuur  =
2
2
2
1
1
1
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
(
)
(
)
x i
y j
z k
x i
y j
z k
+
+
−
+
+
=
2
1
2
1
2
1 ˆ
ˆ
ˆ
(
)
(
)
(
)
x
x i
y
y
j
z
z k
−
+
−
+
−
The magnitude of vector 
1 2
P P
uuuur
 is given by
1 2
P P
uuuur  =
2
2
2
2
1
2
1
2
1
(
)
(
)
(
)
x
x
y
y
z
z
−
+
−
+
−
Fig 10