ExamBro
ExamBro
CUET · MATHS · PYQ PAPER 2023

The values of 'a' for which the vectors \(\vec{\alpha}=\hat{i}+2 \hat{j}+\hat{k}, \vec{\beta}=a \hat{i}+\hat{j}+2 \hat{k}\) and \(\vec{\gamma}=\hat{i}+2 \hat{j}+a \hat{k}\) are coplanar are:

  1. A \(-\frac{1}{2}, 1\)
  2. B \(-1,-\frac{1}{2}\)
  3. C \(1, \frac{1}{2}\)
  4. D \(-1, \frac{1}{2}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(1, \frac{1}{2}\)

Step-by-step Solution

Detailed explanation

Vectors are coplanar if their scalar triple product is zero: \( \begin{vmatrix} 1 & 2 & 1 \\ a & 1 & 2 \\ 1 & 2 & a \end{vmatrix} = 0 \) \(1(a - 4) - 2(a^2 - 2) + 1(2a - 1) = 0\) \(a - 4 - 2a^2 + 4 + 2a - 1 = 0\) \(-2a^2 + 3a - 1 = 0\) \(2a^2 - 3a + 1 = 0\)…
From CUET
Explore more questions on app