vector A • vector B =20 vector A perpendicular vector B then x =?
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Correct option is
B
150
0
2
B
=
A
2
+B
2
+2ABcosθ
....(i)
∴tan90
o
=
A+Bcosθ
Bsinθ
⇒A+Bcosθ=0
∴cosθ=−
B
A
Hence, from (i)
4
B
2
=A
2
+B
2
−2A
2
⇒A=
3
2
B
⇒cosθ=−
B
A
=−
2
3
∴θ=150
o
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