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Let an ant starts from the origin (O) an...

Let an ant starts from the origin (O) and travels 2 units on negative x - axis, 3 units on positive y - axis and travels 3 units on negative z - axis to reach at point A. If `veca=hati-3hatj+2hatk and vecb` be such that the resultant of `veca and vecb` is `3hati-4hatj+hatk`, then `|vec(OA)xx(vecaxx vecb)|^(2)` is equal to

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To solve the problem step by step, we will first determine the position vector of point A, then find the vector B, and finally compute the required expression. ### Step 1: Determine the position vector OA The ant travels as follows: - 2 units on the negative x-axis: This gives us \(-2 \hat{i}\). - 3 units on the positive y-axis: This gives us \(+3 \hat{j}\). - 3 units on the negative z-axis: This gives us \(-3 \hat{k}\). Thus, the position vector \(\vec{OA}\) is: \[ \vec{OA} = -2 \hat{i} + 3 \hat{j} - 3 \hat{k} \] ### Step 2: Given vector A The vector \(\vec{A}\) is given as: \[ \vec{A} = \hat{i} - 3 \hat{j} + 2 \hat{k} \] ### Step 3: Find vector B We know the resultant of vectors \(\vec{A}\) and \(\vec{B}\) is given as: \[ \vec{A} + \vec{B} = 3 \hat{i} - 4 \hat{j} + \hat{k} \] To find \(\vec{B}\), we rearrange the equation: \[ \vec{B} = (3 \hat{i} - 4 \hat{j} + \hat{k}) - \vec{A} \] Substituting \(\vec{A}\): \[ \vec{B} = (3 \hat{i} - 4 \hat{j} + \hat{k}) - (\hat{i} - 3 \hat{j} + 2 \hat{k}) \] Calculating this gives: \[ \vec{B} = (3 - 1) \hat{i} + (-4 + 3) \hat{j} + (1 - 2) \hat{k} = 2 \hat{i} - \hat{j} - \hat{k} \] ### Step 4: Calculate \(|\vec{OA} \times (\vec{A} \times \vec{B})|^2\) We need to find \(\vec{A} \times \vec{B}\) first. The cross product can be calculated using the determinant of a matrix formed by the unit vectors and the components of \(\vec{A}\) and \(\vec{B}\): \[ \vec{A} \times \vec{B} = \begin{vmatrix} \hat{i} & \hat{j} & \hat{k} \\ 1 & -3 & 2 \\ 2 & -1 & -1 \end{vmatrix} \] Calculating this determinant: \[ \vec{A} \times \vec{B} = \hat{i} \begin{vmatrix} -3 & 2 \\ -1 & -1 \end{vmatrix} - \hat{j} \begin{vmatrix} 1 & 2 \\ 2 & -1 \end{vmatrix} + \hat{k} \begin{vmatrix} 1 & -3 \\ 2 & -1 \end{vmatrix} \] Calculating each of these 2x2 determinants: 1. \(\begin{vmatrix} -3 & 2 \\ -1 & -1 \end{vmatrix} = (-3)(-1) - (2)(-1) = 3 + 2 = 5\) 2. \(\begin{vmatrix} 1 & 2 \\ 2 & -1 \end{vmatrix} = (1)(-1) - (2)(2) = -1 - 4 = -5\) 3. \(\begin{vmatrix} 1 & -3 \\ 2 & -1 \end{vmatrix} = (1)(-1) - (-3)(2) = -1 + 6 = 5\) Thus, \[ \vec{A} \times \vec{B} = 5 \hat{i} + 5 \hat{j} + 5 \hat{k} = 5(\hat{i} + \hat{j} + \hat{k}) \] ### Step 5: Now calculate \(\vec{OA} \times (\vec{A} \times \vec{B})\) Using the vector \(\vec{OA} = -2 \hat{i} + 3 \hat{j} - 3 \hat{k}\): \[ \vec{OA} \times (5(\hat{i} + \hat{j} + \hat{k})) = 5 \vec{OA} \times (\hat{i} + \hat{j} + \hat{k}) \] Calculating this cross product: \[ \vec{OA} \times (\hat{i} + \hat{j} + \hat{k}) = \begin{vmatrix} \hat{i} & \hat{j} & \hat{k} \\ -2 & 3 & -3 \\ 1 & 1 & 1 \end{vmatrix} \] Calculating this determinant: \[ = \hat{i} \begin{vmatrix} 3 & -3 \\ 1 & 1 \end{vmatrix} - \hat{j} \begin{vmatrix} -2 & -3 \\ 1 & 1 \end{vmatrix} + \hat{k} \begin{vmatrix} -2 & 3 \\ 1 & 1 \end{vmatrix} \] Calculating each of these 2x2 determinants: 1. \(\begin{vmatrix} 3 & -3 \\ 1 & 1 \end{vmatrix} = (3)(1) - (-3)(1) = 3 + 3 = 6\) 2. \(\begin{vmatrix} -2 & -3 \\ 1 & 1 \end{vmatrix} = (-2)(1) - (-3)(1) = -2 + 3 = 1\) 3. \(\begin{vmatrix} -2 & 3 \\ 1 & 1 \end{vmatrix} = (-2)(1) - (3)(1) = -2 - 3 = -5\) Thus, \[ \vec{OA} \times (\hat{i} + \hat{j} + \hat{k}) = 6 \hat{i} - 1 \hat{j} - 5 \hat{k} \] So, \[ \vec{OA} \times (5(\hat{i} + \hat{j} + \hat{k})) = 5(6 \hat{i} - 1 \hat{j} - 5 \hat{k}) = 30 \hat{i} - 5 \hat{j} - 25 \hat{k} \] ### Step 6: Calculate the magnitude squared Now we need to find the magnitude squared: \[ |\vec{OA} \times (\vec{A} \times \vec{B})|^2 = |30 \hat{i} - 5 \hat{j} - 25 \hat{k}|^2 \] Calculating this: \[ = 30^2 + (-5)^2 + (-25)^2 = 900 + 25 + 625 = 1550 \] ### Final Answer Thus, the value of \(|\vec{OA} \times (\vec{A} \times \vec{B})|^2\) is: \[ \boxed{1550} \]
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