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If veca, vecb are non zero vectors, then...

If `veca, vecb` are non zero vectors, then `((vecaxxvecb)xxveca).((vecbxxveca)xxvecb)` equals

A

`-(veca.vecb)|(vecaxxvecb)|^2`

B

`|vecaxxvecb|^(2)veca^(2)`

C

`|vecaxxvecb|^(2)vecb^(2)`

D

`(veca.vecb)|vecaxxvecb|^(2)`

Text Solution

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The correct Answer is:
To solve the problem, we need to evaluate the expression \(((\vec{a} \times \vec{b}) \times \vec{a}) \cdot ((\vec{b} \times \vec{a}) \times \vec{b})\). ### Step-by-step Solution: 1. **Define the Expression**: Let \( \vec{A} = (\vec{a} \times \vec{b}) \times \vec{a} \) and \( \vec{B} = (\vec{b} \times \vec{a}) \times \vec{b} \). We need to find \( \vec{A} \cdot \vec{B} \). 2. **Use the Vector Triple Product Identity**: The vector triple product identity states that \( \vec{x} \times (\vec{y} \times \vec{z}) = (\vec{x} \cdot \vec{z}) \vec{y} - (\vec{x} \cdot \vec{y}) \vec{z} \). 3. **Calculate \( \vec{A} \)**: \[ \vec{A} = (\vec{a} \times \vec{b}) \times \vec{a} = (\vec{a} \cdot \vec{a}) \vec{b} - (\vec{b} \cdot \vec{a}) \vec{a} \] Simplifying, we have: \[ \vec{A} = |\vec{a}|^2 \vec{b} - (\vec{b} \cdot \vec{a}) \vec{a} \] 4. **Calculate \( \vec{B} \)**: \[ \vec{B} = (\vec{b} \times \vec{a}) \times \vec{b} = (\vec{b} \cdot \vec{b}) \vec{a} - (\vec{a} \cdot \vec{b}) \vec{b} \] Simplifying, we have: \[ \vec{B} = |\vec{b}|^2 \vec{a} - (\vec{a} \cdot \vec{b}) \vec{b} \] 5. **Calculate \( \vec{A} \cdot \vec{B} \)**: Now we compute the dot product: \[ \vec{A} \cdot \vec{B} = \left( |\vec{a}|^2 \vec{b} - (\vec{b} \cdot \vec{a}) \vec{a} \right) \cdot \left( |\vec{b}|^2 \vec{a} - (\vec{a} \cdot \vec{b}) \vec{b} \right) \] 6. **Expand the Dot Product**: Expanding this gives: \[ = |\vec{a}|^2 |\vec{b}|^2 (\vec{b} \cdot \vec{a}) - |\vec{a}|^2 (\vec{b} \cdot \vec{b}) \vec{a} \cdot \vec{a} - (\vec{b} \cdot \vec{a})^2 \vec{a} \cdot \vec{b} + (\vec{b} \cdot \vec{a})^2 \vec{b} \cdot \vec{b} \] 7. **Combine Like Terms**: Notice that terms can be rearranged and simplified: \[ = |\vec{a}|^2 |\vec{b}|^2 (\vec{b} \cdot \vec{a}) - |\vec{a}|^2 |\vec{b}|^2 - (\vec{b} \cdot \vec{a})^2 + (\vec{b} \cdot \vec{a})^2 \] The last two terms cancel out. 8. **Final Result**: Thus, we have: \[ \vec{A} \cdot \vec{B} = |\vec{a}|^2 |\vec{b}|^2 (\vec{b} \cdot \vec{a}) - |\vec{a}|^2 |\vec{b}|^2 = 0 \] ### Conclusion: The final result is: \[ \boxed{0} \]

To solve the problem, we need to evaluate the expression \(((\vec{a} \times \vec{b}) \times \vec{a}) \cdot ((\vec{b} \times \vec{a}) \times \vec{b})\). ### Step-by-step Solution: 1. **Define the Expression**: Let \( \vec{A} = (\vec{a} \times \vec{b}) \times \vec{a} \) and \( \vec{B} = (\vec{b} \times \vec{a}) \times \vec{b} \). We need to find \( \vec{A} \cdot \vec{B} \). 2. **Use the Vector Triple Product Identity**: ...
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OBJECTIVE RD SHARMA ENGLISH-SCALAR AND VECTOR PRODUCTS OF THREE VECTORS -Section I - Solved Mcqs
  1. If veca bot vecb then vector vecv in terms of veca and vecb satisfying...

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  2. Find the value of a so that the volume of the parallelopiped formed b...

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  3. let veca , vecb and vecc be three vectors having magnitudes 1, 1 and 2...

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  4. If vecA , vecB and vecC are vectors such that |vecB| = |vecC| prove th...

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  5. If the magnitude of the moment about the pont hatj+hatk of a force hat...

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  6. If the volume of parallelopiped formed by the vectors a,b,c as three c...

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  7. If |veca|=5, |vecb|=3, |vecc|=4 and veca is perpendicular to vecb and ...

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

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  9. Prove that (veca.(vecbxxhati))hati+(veca.(vecbxxhatj))hatj+ (veca.(vec...

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  10. The unit vector which is orhtogonal to the vector 3hati+2hatj+6hatk an...

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  11. Let veca, vecb and vecc be non-zero vectors such that (veca xx vecb) x...

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  12. vecp, vecq and vecr are three mutually prependicular vectors of the sa...

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  13. If veca and vecb are vectors in space given by veca= (hati-2hatj)/sqrt...

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  14. Two adjacent sides of a parallelogram A B C D are given by vec A B=...

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  15. Let a=hat(j)-hat(k) and b=hat(i)-hat(j)-hat(k). Then, the vector v sat...

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  16. The vector(s) which is /are coplanar with vectors hati +hatj + 2hatk a...

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  17. Let veca=-hati-hatk,vecb =-hati + hatj and vecc = i + 2hatj + 3hatk be...

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  18. veca =1/sqrt(10)(3hati + hatk) and vecb =1/7(2hati +3hatj-6hatk), then...

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  19. If veca=hati-2hatj+3hatk, vecb=2hati+3hatj-hatk and vecc=rhati+hatj+(2...

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  20. If veca, vecb are non zero vectors, then ((vecaxxvecb)xxveca).((vecbxx...

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