THEOREM.
(a)For the definition
cos 
=(1,0)
=(1,0)
Therefore
From the definition
cos 
cos 90
x 0
Therefore
– Suppose the vector
= 
= 
+
+
+
=
From the definition
= cos 
= cos 
– Consider the vector
QUESTIONS
1. If 
+ 2
+2
Find the angle between 
and 
2. Show that the vectors
=
are orthogonal
3. If 
=2, 
=3
, find 
4. The vectors 
and
where k
are such that
and 
are orthogonal find k
5. If 
and
= 
Find the value of 
if 
and 
are orthogonal
6.If 
=2, 
=3, 
Find 
APPLICATION OF DOT PRODUCT
1. TO VERIFY COSINE RULE
Consider the vector diagram below
+
= 
…………………..(i)
Dot by 
.
=
= 
= 
+
