The vector →a=α^i+2^j+β^k lies in the plane of vectors →b=^i+^j, and →c=^j+^k and bisect the angle between →b and →c then which one of the following gives possible values of α and β ?
A
α=1,β=2
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B
α=2,β=1
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C
β=α=1
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D
α=β=2
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Solution
The correct option is Bβ=α=1 As vector ¯a lies in the plane of ¯b & ¯c
∴[¯a¯b¯c]=0⇒∣∣
∣∣α2β110011∣∣
∣∣=0⇒α+β=0....(1)
Again ¯a bisect the angle between ¯b and ¯c ∴¯a⋅¯b=¯a⋅¯c ⇒α+2=β+2⇒α=β....(2)