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Scalar Triple Product Properties

Mediummathematics

If the scalar triple product [a b c] equals 7 for three given vectors, what is the value of the rearranged product [b c a]?

Select the correct option:

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About This Question

Subject
mathematics
Chapter
vector algebra
Topic
scalar triple product properties
Difficulty
Medium
Year
2025
Tags
advanced-calculus-drillscalar-triple-productcyclic-permutationdeterminant-symmetrysign-properties

Solution

Correct Answer:

The scalar triple product is invariant under cyclic permutation of its vectors, meaning [a b c] = [b c a] = [c a b], while any single swap of two vectors reverses its sign. This permutation symmetry is a heavily tested JEE Advanced property rooted in determinant behavior. Moving from [a b c] to [b c a] is a cyclic shift, advancing each vector one position with a wraparound, which preserves the value entirely; therefore [b c a] = [a b c] = 7. Option -7 would arise only from a single transposition such as [b a c], which is a non-cyclic swap, not the cyclic rotation given here. Option 0 would require the vectors to be coplanar, contradicting the nonzero value 7. Option 14 doubles the product with no justification. The underlying reason is that a cyclic permutation of determinant rows corresponds to an even permutation, leaving the determinant unchanged. Plausibility check: a cyclic shift can be built from two successive row swaps, and two sign reversals multiply to +1, so the value must remain 7, consistent with the result.

This medium difficulty mathematics question is from the chapter vector algebra, covering the topic of scalar triple product properties. It appeared in the 2025 exam.

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