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JEE Mains 05-Sep-2020 Shift 2 Solved Paper
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© examsnet.com
Question : 75
Total: 75
Let the vectors
→
a
,
→
b
,
→
c
be such that
|
→
a
|
=
2
,
|
→
b
|
=
4
and
|
→
c
|
=
4
.
If the projection of
→
b
on
→
a
is equal to the projection of
→
c
on
→
a
and
→
b
is perpendicular to
→
c
,
then the value of
|
→
a
+
→
b
−
→
c
|
is ______.
Your Answer:
Validate
Solution:
Projection of
→
b
on
→
a
=
projection of
→
c
on
→
a
⇒
→
b
.
→
a
|
→
a
|
=
→
c
.
→
a
|
→
a
|
⇒
→
b
.
→
a
=
→
c
.
→
a
because
→
b
is perpendicular to
→
c
⇒
→
b
.
→
c
=
0
Let
|
→
a
+
→
b
−
→
c
|
=
k
Square both sides
k
2
=
→
a
2
+
→
b
2
+
→
c
2
+
2
→
a
.
→
b
−
2
→
a
.
→
c
−
2
→
b
.
→
c
k
2
=
→
a
2
+
→
b
2
+
→
c
2
=
36
k
=
6
=
|
→
a
+
→
b
−
→
c
|
© examsnet.com
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