11. If the sum of two unit vectors is also a unit vector,
then magnitude of their difference and angle
between the two given unit vectors is
(1) 3,60
(2) 3,120°
(3) 2,60
(4) 2,120°
Answers
Answered by
2
Correct option is
B
3
,120
∘
∣
a
+
b
∣=1
∣
a
∣
2
+∣
b
∣
2
+2∣
a
∣∣
b
∣cosθ
=1
→2(1+cosθ)=1
→cosθ=
2
−1
θ=120
∘
∣
a
+
b
∣=
∣
a
∣+∣
b
∣
2
−2∣
a
∣∣
b
∣cosθ
=
1+1−2cos120
∘
=
2+2×
2
1
=
3
.
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