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NDA Math Vector Algebra
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© examsnet.com
Question : 32
Total: 101
What is the scalar projection of
→
a
=
⋀
i
−
2
⋀
j
+
⋀
k
on
→
b
=
4
⋀
i
−
4
⋀
j
+
7
⋀
k
?
[NDA II 2019]
√
6
9
19
9
9
19
√
6
19
Validate
Solution:
We know that, projection of
→
a
and
→
b
=
→
a
⋅
→
b
|
→
b
|
Here,
→
a
=
→
i
−
2
→
j
+
→
k
and
→
b
=
4
→
i
−
4
→
j
+
7
→
k
∴
→
a
⋅
→
b
=
(
→
i
−
2
→
j
+
→
k
)
⋅
(
4
→
i
−
4
→
j
+
7
→
k
)
=
1
(
4
)
+
(
–
2
)
(
–
4
)
+
1
(
7
)
=
4
+
8
+
7
=
19
and
|
→
b
|
=
√
4
2
+
(
−
4
)
2
+
7
2
=
√
16
+
16
+
49
=
√
81
=
9
Hence, projection of
→
a
on
→
b
=
→
a
⋅
→
b
|
→
b
|
=
19
9
© examsnet.com
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