MCQ
Let $\alpha, \beta, \gamma$ be distinct real numbers. The points with position vectors $\alpha \hat{i}+\beta \hat{j}+\gamma \dot{k}$, $\beta \hat{i}+\gamma \hat{j}+\alpha \hat{k}, \gamma \hat{i}+\alpha \hat{j}+\beta \hat{k}$
  • A
    Are collinear
  • Form an equilateral triangle
  • C
    Form a scalene triangle
  • D
    Form a right angled triangle

Answer

Correct option: B.
Form an equilateral triangle
(B) Let $P , Q$ and R be points having position vectors $\alpha \hat{ i }+\beta \hat{ j }+\gamma \hat{ k }, \beta \hat{ i }+\gamma \hat{ j }+\alpha \hat{ k }$ and $\gamma \hat{ i }+\alpha \hat{ j }+\beta \hat{ k }$
Then, $|\overline{ PQ }|=|\overline{ QR }|=|\overline{ RP }|$
$=\sqrt{(\alpha-\beta)^2+(\beta-\gamma)^2+(\gamma-\alpha)^2}$
Hence, $\triangle PQR$ is an equilateral triangle.

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