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Byju's Answer
Standard XII
Mathematics
Applications of Dot Product
If |a + b| ...
Question
If
∣
∣
∣
→
a
+
→
b
∣
∣
∣
=
∣
∣
∣
→
a
−
→
b
∣
∣
∣
, prove that
→
a
and
→
b
are perpendicular.
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Solution
Given
∣
∣
∣
→
a
+
→
b
∣
∣
∣
=
∣
∣
∣
→
a
−
→
b
∣
∣
∣
Square on both sides
∣
∣
∣
→
a
+
→
b
∣
∣
∣
2
=
∣
∣
∣
→
a
−
→
b
∣
∣
∣
2
cos
(
→
a
,
→
b
)
⇒
∣
∣
→
a
∣
∣
2
+
∣
∣
∣
→
b
∣
∣
∣
2
+
2
∣
∣
→
a
∣
∣
∣
∣
∣
→
b
∣
∣
∣
cos
(
→
a
,
→
b
)
=
∣
∣
→
a
∣
∣
2
+
∣
∣
∣
→
b
∣
∣
∣
2
−
2
∣
∣
→
a
∣
∣
∣
∣
∣
→
b
∣
∣
∣
cos
(
→
a
,
→
b
)
cos
(
→
a
,
→
b
)
=
0
∴
angle between
→
a
,
→
b
=
π
2
Suggest Corrections
0
Similar questions
Q.
If
∣
∣
∣
→
a
+
→
b
∣
∣
∣
=
∣
∣
∣
→
a
−
→
b
∣
∣
∣
,
then prove that
→
a
and
→
b
are mutually perpendicular vectors.
Q.
Prove that
(
a
+
b
)
.
(
a
+
b
)
=
|
a
|
2
+
|
b
|
2
, if and only if a, b are perpendicular, given
a
≠
0
,
b
≠
0
Q.
If
→
a
and
→
b
are two vectors such that
|
→
a
+
→
b
|
=
|
→
a
|
, then prove that vector
2
→
a
+
→
b
is perpendicular to vector
→
b
.
Q.
If
a
→
,
b
→
are two vectors such that
a
→
+
b
→
=
b
→
, then prove that
a
→
+
2
b
→
is perpendicular to
a
→
.
Q.
For three vectors
→
a
,
→
b
and
→
c
i
f
→
a
×
→
b
=
→
c
a
n
d
→
a
×
→
c
=
→
b
,then prove that
→
a
,
→
b
a
n
d
→
c
are mutually perpendicular vectors,
|
→
b
|
=
|
→
a
|
a
n
d
|
→
a
|
=
1
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