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If veca, vecb, vecc are any three non co...

If `veca, vecb, vecc` are any three non coplanar vectors, then
`(veca+vecb+vecc).(vecb+vecc)xx(vecc+veca)`

A

`0`

B

`[(veca, vecb, vecc)]`

C

`2[(veca, vecb, vecc)]`

D

`3[(veca, vecb, vecc)]`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to evaluate the expression \((\vec{a} + \vec{b} + \vec{c}) \cdot ((\vec{b} + \vec{c}) \times (\vec{c} + \vec{a}))\). ### Step-by-step Solution: 1. **Start with the expression**: \[ (\vec{a} + \vec{b} + \vec{c}) \cdot ((\vec{b} + \vec{c}) \times (\vec{c} + \vec{a})) \] 2. **Expand the cross product**: We need to compute \((\vec{b} + \vec{c}) \times (\vec{c} + \vec{a})\). Using the distributive property of the cross product, we have: \[ (\vec{b} + \vec{c}) \times (\vec{c} + \vec{a}) = \vec{b} \times \vec{c} + \vec{b} \times \vec{a} + \vec{c} \times \vec{c} + \vec{c} \times \vec{a} \] Since \(\vec{c} \times \vec{c} = \vec{0}\) (the cross product of any vector with itself is zero), this simplifies to: \[ \vec{b} \times \vec{c} + \vec{b} \times \vec{a} + \vec{c} \times \vec{a} \] 3. **Substitute back into the dot product**: Now substitute this back into the original expression: \[ (\vec{a} + \vec{b} + \vec{c}) \cdot (\vec{b} \times \vec{c} + \vec{b} \times \vec{a} + \vec{c} \times \vec{a}) \] 4. **Distribute the dot product**: We can distribute the dot product: \[ = (\vec{a} + \vec{b} + \vec{c}) \cdot (\vec{b} \times \vec{c}) + (\vec{a} + \vec{b} + \vec{c}) \cdot (\vec{b} \times \vec{a}) + (\vec{a} + \vec{b} + \vec{c}) \cdot (\vec{c} \times \vec{a}) \] 5. **Evaluate each term**: - The first term: \((\vec{a} + \vec{b} + \vec{c}) \cdot (\vec{b} \times \vec{c})\) can be broken down: - \(\vec{a} \cdot (\vec{b} \times \vec{c}) + \vec{b} \cdot (\vec{b} \times \vec{c}) + \vec{c} \cdot (\vec{b} \times \vec{c})\) - The second and third terms are zero since the dot product of a vector with a vector perpendicular to it is zero. Thus, this term simplifies to: \[ \vec{a} \cdot (\vec{b} \times \vec{c}) \] - The second term: \((\vec{a} + \vec{b} + \vec{c}) \cdot (\vec{b} \times \vec{a})\) simplifies similarly: - \(\vec{a} \cdot (\vec{b} \times \vec{a}) + \vec{b} \cdot (\vec{b} \times \vec{a}) + \vec{c} \cdot (\vec{b} \times \vec{a})\) - The first and second terms are zero, so this simplifies to: \[ \vec{c} \cdot (\vec{b} \times \vec{a}) \] - The third term: \((\vec{a} + \vec{b} + \vec{c}) \cdot (\vec{c} \times \vec{a})\) simplifies to: - \(\vec{a} \cdot (\vec{c} \times \vec{a}) + \vec{b} \cdot (\vec{c} \times \vec{a}) + \vec{c} \cdot (\vec{c} \times \vec{a})\) - The first and third terms are zero, so this simplifies to: \[ \vec{b} \cdot (\vec{c} \times \vec{a}) \] 6. **Combine the results**: Now we combine the results from all three terms: \[ \vec{a} \cdot (\vec{b} \times \vec{c}) + \vec{c} \cdot (\vec{b} \times \vec{a}) + \vec{b} \cdot (\vec{c} \times \vec{a}) \] 7. **Recognize the scalar triple product**: The expression we have is the scalar triple product: \[ \vec{a} \cdot (\vec{b} \times \vec{c}) = \vec{b} \cdot (\vec{c} \times \vec{a}) = \vec{c} \cdot (\vec{a} \times \vec{b}) \] Hence, the final result is: \[ \text{Result} = \vec{a} \cdot (\vec{b} \times \vec{c}) = \text{Volume of the parallelepiped formed by } \vec{a}, \vec{b}, \vec{c} \] ### Final Answer: \[ (\vec{a} + \vec{b} + \vec{c}) \cdot ((\vec{b} + \vec{c}) \times (\vec{c} + \vec{a})) = \vec{a} \cdot (\vec{b} \times \vec{c}) \]

To solve the problem, we need to evaluate the expression \((\vec{a} + \vec{b} + \vec{c}) \cdot ((\vec{b} + \vec{c}) \times (\vec{c} + \vec{a}))\). ### Step-by-step Solution: 1. **Start with the expression**: \[ (\vec{a} + \vec{b} + \vec{c}) \cdot ((\vec{b} + \vec{c}) \times (\vec{c} + \vec{a})) \] ...
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OBJECTIVE RD SHARMA ENGLISH-SCALAR AND VECTOR PRODUCTS OF THREE VECTORS -Section I - Solved Mcqs
  1. If vecb is a unit vector, then (veca. vecb)vecb+vecbxx(vecaxxvecb) is ...

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  2. If veca, vecb, vecc are any three non coplanar vectors, then [(veca+ve...

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  3. If veca, vecb, vecc are any three non coplanar vectors, then (veca+v...

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  4. Let veca, vecb and vecc be three having magnitude 1,1 and 2 respective...

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  5. If veca = (hati + hatj +hatk), veca. vecb= 1 and vecaxxvecb = hatj -ha...

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  6. If veca, vecb, vecc are non-coplanar non-zero vectors, then (vecaxxv...

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  7. If the vectors veca, vecb, vecc and vecd are coplanar vectors, then (...

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  8. (vecaxxvecb).(veccxxvecd) is not equal to

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  9. Let veca = 2hati + hatj + hatk, and vecb = hati+ hatj if c is a vecto...

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  10. If veca,vecb and vecc are three non coplanar vectors and vecr is any v...

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  11. The number of faces of a triangular pyramid or tetrahedron is .

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  12. The acute angle that the vector 2hati-2hatj+hatk makes with the plane ...

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  13. If veca, vecb, vecc are non-null non coplanar vectors, then [(veca-2...

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  14. The three vectors hat i+hat j,hat j+hat k, hat k+hat i taken two at a ...

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  15. Let G(1), G(2) and G(3) be the centroid of the triangular faces OBC, O...

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  16. Let vecr, veca, vecb and vecc be four non -zero vectors such that vecr...

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  17. Let vecV = 2hati +hatj - hatk and vecW= hati + 3hatk . if vecU is a u...

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  18. If a and b are unit vectors, then the vector defined as V=(a+b)times(a...

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  19. If vec(alpha)=2hati+3hatj-hatk, vec(beta)=-hati+2hatj-4hatk, vecgamma=...

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  20. Let alpha = a hati + b hatj + chatk , vecbeta = bhati + chatj + ahatk ...

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