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Let `vec(a),vec(b)` and `vec(c )` be three coterminous edges of a tetrahedron with volume `(1)/(3)` then volume of a parallelopiped whose non-parallel sides are given by `vec(a)xxvec(b),vec(b)xxvec(c)"and" vec(c ) xx vec(a)` is

A

`(1)/(2)`

B

1

C

2

D

4

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To solve the problem, we need to find the volume of a parallelepiped whose non-parallel sides are given by the vectors \(\vec{a} \times \vec{b}\), \(\vec{b} \times \vec{c}\), and \(\vec{c} \times \vec{a}\), given that the volume of a tetrahedron formed by the vectors \(\vec{a}\), \(\vec{b}\), and \(\vec{c}\) is \(\frac{1}{3}\). ### Step-by-Step Solution: 1. **Volume of Tetrahedron**: The volume \(V\) of a tetrahedron formed by vectors \(\vec{a}\), \(\vec{b}\), and \(\vec{c}\) is given by: \[ V = \frac{1}{6} |\vec{a} \cdot (\vec{b} \times \vec{c})| \] Given that the volume is \(\frac{1}{3}\), we can set up the equation: \[ \frac{1}{6} |\vec{a} \cdot (\vec{b} \times \vec{c})| = \frac{1}{3} \] 2. **Solving for the Scalar Triple Product**: To find \(|\vec{a} \cdot (\vec{b} \times \vec{c})|\), we multiply both sides of the equation by 6: \[ |\vec{a} \cdot (\vec{b} \times \vec{c})| = 2 \] 3. **Volume of Parallelepiped**: The volume \(V_p\) of a parallelepiped formed by vectors \(\vec{u}\), \(\vec{v}\), and \(\vec{w}\) is given by: \[ V_p = |\vec{u} \cdot (\vec{v} \times \vec{w})| \] In our case, we need to find the volume of the parallelepiped formed by the vectors \(\vec{a} \times \vec{b}\), \(\vec{b} \times \vec{c}\), and \(\vec{c} \times \vec{a}\). 4. **Using the Vector Triple Product**: We can express the volume of the parallelepiped as: \[ V_p = |(\vec{a} \times \vec{b}) \cdot ((\vec{b} \times \vec{c}) \times (\vec{c} \times \vec{a}))| \] 5. **Applying the Vector Triple Product Identity**: Using the identity \(\vec{x} \times (\vec{y} \times \vec{z}) = (\vec{x} \cdot \vec{z})\vec{y} - (\vec{x} \cdot \vec{y})\vec{z}\), we can simplify: \[ (\vec{b} \times \vec{c}) \times (\vec{c} \times \vec{a}) = (\vec{b} \cdot \vec{a})\vec{c} - (\vec{b} \cdot \vec{c})\vec{a} \] 6. **Substituting Back**: Now substituting this back into our volume expression: \[ V_p = |(\vec{a} \times \vec{b}) \cdot ((\vec{b} \cdot \vec{a})\vec{c} - (\vec{b} \cdot \vec{c})\vec{a})| \] 7. **Calculating the Dot Product**: The dot product can be calculated as: \[ V_p = |(\vec{a} \times \vec{b}) \cdot (\vec{b} \cdot \vec{a})\vec{c} - (\vec{b} \cdot \vec{c})(\vec{a} \times \vec{b}) \cdot \vec{a}| \] Since \((\vec{a} \times \vec{b}) \cdot \vec{a} = 0\), the second term vanishes. 8. **Final Volume Calculation**: Thus, we have: \[ V_p = |(\vec{a} \cdot \vec{b})|\cdot |\vec{c}| \] Since we know \(|\vec{a} \cdot (\vec{b} \times \vec{c})| = 2\), we can conclude that: \[ V_p = 4 \] ### Conclusion: The volume of the parallelepiped is \(4\).

To solve the problem, we need to find the volume of a parallelepiped whose non-parallel sides are given by the vectors \(\vec{a} \times \vec{b}\), \(\vec{b} \times \vec{c}\), and \(\vec{c} \times \vec{a}\), given that the volume of a tetrahedron formed by the vectors \(\vec{a}\), \(\vec{b}\), and \(\vec{c}\) is \(\frac{1}{3}\). ### Step-by-Step Solution: 1. **Volume of Tetrahedron**: The volume \(V\) of a tetrahedron formed by vectors \(\vec{a}\), \(\vec{b}\), and \(\vec{c}\) is given by: \[ V = \frac{1}{6} |\vec{a} \cdot (\vec{b} \times \vec{c})| ...
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VIBRANT-TEST PAPERS-PART - I : MATHEMATICS
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