**Question :**A= 3î− ĵ+ 7k̂ and B = 5î− ĵ+ 9k̂ the direction cosine m of the vector A+ B is

(A) zero

(B) \dfrac{3}{\sqrt{31}}

(C) \dfrac{9}{\sqrt{107}}

(D) 5

**Answer :** option (A)

**Solution :**

with
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**Question :**A= 3î− ĵ+ 7k̂ and B = 5î− ĵ+ 9k̂ the direction cosine m of the vector A+ B is

(A) zero

(B) \dfrac{3}{\sqrt{31}}

(C) \dfrac{9}{\sqrt{107}}

(D) 5

**Answer :** option (A)

**Solution :**