Question

Vector r which is equally inclined to coordinate axes such that |r| = 15√3 is

(A) i + j + k

(B)15(i + j + k)

(C) 7(i + j + k)

(D) of these

Answer 1

Correct option (B)15(i + j + k)

Explanation:

I2 + m2 + n2 = 1

or cos2α + cos2β + cos2γ = 1

or 3cos2θ = 1 or cosθ = 1/3

∴ The desired vector is

15√3(1/√3i + 1/√3j + 1/√3k) = 15(i + j + k)