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Which of the following statements are correct?

(A) The angle between the vectors with direction ratios proportional to -3, 5, 4 and 4, 5, 3 is π3\dfrac{\pi}{3}

(B) The direction cosines of Y-axis is 0, 1, 0.

(C) The cartesian equation of a line is 3x−6=2y+1=2z−13x-6=2y+1=2z-1, then its direction ratios are proportional to 2, 2, 3

(D) The vector equation of the line passing through the point (2,−1,−1)(2,-1,-1) and direction ratios 1, 2, 3 is r⃗=(2i^−j^−k^)+λ(i^+2j^+3k^)\vec r=(2\hat i-\hat j-\hat k)+\lambda(\hat i+2\hat j+3\hat k)

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 1

(A) cos⁡θ=−12+25+125050=12\cos\theta = \dfrac{-12+25+12}{\sqrt{50}\sqrt{50}} = \dfrac{1}{2}, so θ=π3\theta = \dfrac{\pi}{3}: correct.

(B) Correct by definition.

(C) Rewriting as x−21/3=y+1/21/2=z−1/21/2\dfrac{x-2}{1/3} = \dfrac{y+1/2}{1/2} = \dfrac{z-1/2}{1/2} gives direction ratios 2,3,32,3,3, not 2,2,32,2,3: incorrect.

(D) Correct form of the vector equation.

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