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If veca,vecb are non-collinear vectors, ...

If `veca,vecb` are non-collinear vectors, then
`[(veca,vecb,hati)]hati+[(veca,vecb,hatj)]hatj+[(veca,vecb,hatk)]hatk=`

A

`veca+vecb`

B

`vecaxxvecb`

C

`veca-vecb`

D

`vecbxxveca`

Text Solution

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The correct Answer is:
To solve the problem, we need to evaluate the expression given in the question: \[ [(\vec{a}, \vec{b}, \hat{i})] \hat{i} + [(\vec{a}, \vec{b}, \hat{j})] \hat{j} + [(\vec{a}, \vec{b}, \hat{k})] \hat{k} \] where \((\vec{a}, \vec{b}, \hat{i})\) denotes the scalar triple product of vectors \(\vec{a}\), \(\vec{b}\), and \(\hat{i}\). ### Step-by-step Solution: 1. **Understanding Scalar Triple Product**: The scalar triple product of three vectors \(\vec{x}, \vec{y}, \vec{z}\) can be expressed as: \[ (\vec{x}, \vec{y}, \vec{z}) = \vec{x} \cdot (\vec{y} \times \vec{z}) \] We will apply this property to our expression. 2. **Rewriting Each Term**: We can rewrite each term in the expression using the property of the scalar triple product: \[ [(\vec{a}, \vec{b}, \hat{i})] = \vec{a} \cdot (\vec{b} \times \hat{i}) \] \[ [(\vec{a}, \vec{b}, \hat{j})] = \vec{a} \cdot (\vec{b} \times \hat{j}) \] \[ [(\vec{a}, \vec{b}, \hat{k})] = \vec{a} \cdot (\vec{b} \times \hat{k}) \] 3. **Substituting Back**: Substitute these back into the original expression: \[ \vec{a} \cdot (\vec{b} \times \hat{i}) \hat{i} + \vec{a} \cdot (\vec{b} \times \hat{j}) \hat{j} + \vec{a} \cdot (\vec{b} \times \hat{k}) \hat{k} \] 4. **Assuming \(\vec{a} \times \vec{b}\)**: Let’s denote \(\vec{a} \times \vec{b} = \vec{c}\), where \(\vec{c} = x \hat{i} + y \hat{j} + z \hat{k}\) for some components \(x, y, z\). 5. **Dot Products**: Now, we can express the dot products: \[ \vec{a} \cdot (\vec{b} \times \hat{i}) = \text{component of } \vec{c} \text{ along } \hat{i} = x \] \[ \vec{a} \cdot (\vec{b} \times \hat{j}) = \text{component of } \vec{c} \text{ along } \hat{j} = y \] \[ \vec{a} \cdot (\vec{b} \times \hat{k}) = \text{component of } \vec{c} \text{ along } \hat{k} = z \] 6. **Final Expression**: Therefore, substituting these back, we get: \[ x \hat{i} + y \hat{j} + z \hat{k} = \vec{c} = \vec{a} \times \vec{b} \] Thus, the final result is: \[ [(\vec{a}, \vec{b}, \hat{i})] \hat{i} + [(\vec{a}, \vec{b}, \hat{j})] \hat{j} + [(\vec{a}, \vec{b}, \hat{k})] \hat{k} = \vec{a} \times \vec{b} \] ### Conclusion: The value of the given expression is \(\vec{a} \times \vec{b}\). ---

To solve the problem, we need to evaluate the expression given in the question: \[ [(\vec{a}, \vec{b}, \hat{i})] \hat{i} + [(\vec{a}, \vec{b}, \hat{j})] \hat{j} + [(\vec{a}, \vec{b}, \hat{k})] \hat{k} \] where \((\vec{a}, \vec{b}, \hat{i})\) denotes the scalar triple product of vectors \(\vec{a}\), \(\vec{b}\), and \(\hat{i}\). ...
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OBJECTIVE RD SHARMA ENGLISH-SCALAR AND VECTOR PRODUCTS OF THREE VECTORS -Exercise
  1. If veca=2hati-3hatj+5hatk , vecb=3hati-4hatj+5hatk and vecc=5hati-3hat...

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  2. If veca,vecb,vecc are linearly independent vectors, then ((veca+2vecb)...

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  3. If veca,vecb are non-collinear vectors, then [(veca,vecb,hati)]hati+[...

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  4. If [(2veca+4vecb,vecc,vecd)]=lamda[(veca,vecc,vecd)]+mu[(vecb,vecc,vec...

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  5. If the volume of the tetrahedron whose vertices are (1,-6,10),(-1,-3,7...

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  6. (vecbxxvecc)xx(veccxxveca)=

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  7. When a right handed rectangular Cartesian system OXYZ is rotated about...

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  8. Prove that vectors vecu=(al+a(1)l(1))hati+(am+a(1)m(1))hatj + (an+a(...

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  9. If vecaxx(vecaxxvecb)=vecbxx(vecbxxvecc) and veca.vecb!=0, then [(veca...

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  10. [(veca,vecb,axxvecb)]+(veca.vecb)^(2)=

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  11. Let vec(alpha),vec(beta) and vec(gamma be the unit vectors such that v...

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  12. If veca, vecb and vecc are unit coplanar vectors, then [(2veca-3vecb,...

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  13. If [(veca,vecb,vecc)]=3, then the volume (in cubic units) of the paral...

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  14. If V is the volume of the parallelepiped having three coterminous edge...

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  15. Unit vectors veca and vecb ar perpendicular , and unit vector vecc is ...

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  16. If vectors vec A B=-3 hat i+4 hat ka n d vec A C=5 hat i-2 hat j+4 ha...

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  17. Let the position vectors of vertices A,B,C of DeltaABC be respectively...

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  18. The position vector of a point P is vecr=xhati+yhatj+zhatk where x,y,z...

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  19. veca and vecb are two unit vectors that are mutually perpendicular. A...

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  20. If the vectors 2ahati+bhatj+chatk, bhati+chatj+2ahatk and chati+2ahatj...

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