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Byju's Answer
Standard XII
Mathematics
Addition of Vectors
If R⃗ = A⃗ ...
Question
If
→
R
=
(
→
A
+
→
B
)
,
Show that
R
2
=
A
2
+
B
2
+
2
A
B
c
o
s
θ
Open in App
Solution
∣
∣
¯
¯¯
¯
R
∣
∣
2
=
¯
¯¯
¯
R
.
R
⟹
∣
∣
¯
¯¯
¯
R
∣
∣
2
=
(
¯
¯¯
¯
A
+
¯
¯¯
¯
B
)
.
(
¯
¯¯
¯
A
+
¯
¯¯
¯
B
)
⟹
∣
∣
¯
¯¯
¯
R
∣
∣
2
=
¯
¯¯
¯
A
.
¯
¯¯
¯
A
+
¯
¯¯
¯
A
.
¯
¯¯
¯
B
+
¯
¯¯
¯
B
.
¯
¯¯
¯
A
+
¯
¯¯
¯
B
.
¯
¯¯
¯
B
(
¯
¯¯
¯
A
.
¯
¯¯
¯
B
=
¯
¯¯
¯
B
.
¯
¯¯
¯
A
(
f
o
r
d
o
t
p
r
o
d
u
c
t
)
)
⟹
∣
∣
¯
¯¯
¯
R
∣
∣
2
=
∣
∣
¯
¯¯
¯
A
∣
∣
.
∣
∣
¯
¯¯
¯
A
∣
∣
cos
(
0
)
+
∣
∣
¯
¯¯
¯
A
∣
∣
.
∣
∣
¯
¯¯
¯
B
∣
∣
cos
θ
+
∣
∣
¯
¯¯
¯
B
∣
∣
.
∣
∣
¯
¯¯
¯
A
∣
∣
cos
θ
+
∣
∣
¯
¯¯
¯
B
∣
∣
.
∣
∣
¯
¯¯
¯
B
∣
∣
cos
(
0
)
⟹
∣
∣
¯
¯¯
¯
R
∣
∣
2
=
∣
∣
¯
¯¯
¯
A
∣
∣
2
+
∣
∣
¯
¯¯
¯
B
∣
∣
2
+
2
∣
∣
¯
¯¯
¯
A
∣
∣
.
∣
∣
¯
¯¯
¯
B
∣
∣
cos
θ
(
w
h
e
r
e
∣
∣
¯
¯¯
¯
R
∣
∣
2
i
s
d
o
t
p
r
o
d
u
c
t
o
f
R
.
R
o
r
∣
∣
¯
¯¯
¯
R
∣
∣
2
)
Suggest Corrections
1
Similar questions
Q.
Given that
→
A
+
→
B
=
→
R
and
A
2
+
B
2
=
R
2
.The angle between
→
A
and
→
B
is
Q.
If
→
r
×
→
a
=
→
b
×
→
a
;
→
r
×
→
b
=
→
a
×
→
b
;
→
a
≠
0
,
→
b
≠
0
,
→
a
≠
λ
→
b
;
→
a
is not perpendicular to
→
b
, then
→
r
=
Q.
Assertion :If
→
r
×
→
a
=
→
b
,
→
r
.
→
a
=
1
,
then
→
r
=
→
a
+
→
a
×
→
b
.
Reason: The solution of the
→
r
×
→
a
=
→
b
is
→
r
=
→
a
×
→
b
.
Q.
If
→
a
=
→
i
+
→
j
,
→
b
=
2
→
j
−
→
k
and
→
r
×
→
a
=
→
b
×
→
a
,
→
r
×
→
b
=
→
a
×
→
b
, then
→
r
|
→
r
|
is equal to
Q.
If
→
a
,
→
b
,
→
c
are three non-coplanar non-zero vectors and
→
r
is any vector, then
(
→
a
×
→
b
)
×
(
→
r
×
→
c
)
+
(
→
b
×
→
c
)
×
(
→
r
×
→
a
)
+
(
→
c
×
→
a
)
×
(
→
r
×
→
b
)
=
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