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Vectors A  and  B  include  an  angle  θ  between  them.   If  (A+B)  and  (AB)  respectively subtend angles α and β with A, then (tanα+tanβ) is

a
(AB sinθ)(A2+B2cos2θ)
b
(2 AB sinθ)(A2-B2cos2θ)
c
(A2sin2θ)(A2+B2cos2θ)
d
(B2sin2θ)(A2-B2cos2θ)

detailed solution

Correct option is B

tanα = BsinθA+Bcosθ ------(i)Where α is the angle made by the vector (A→ +B→)  with  A→Similarly, tanβ = BsinθA-Bcosθ   -------(ii)Where β is the angle made by the vector (A→ − B→)  with  A→Note that the angle between A→  and (− B→) is (1800)-θAdding (i) and (ii), we gettanα +tanβ = BsinθA+Bcosθ+BsinθA-Bcosθ =(AB sinθ −B2sinθcosθ+ABsinθ+B2sinθcosθ(A+Bcosθ)(A−Bcosθ)= 2ABsinθ(A2-B2cos2θ)

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