GATE CE 2024 Set 2 — Question 44
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Engineering Mathematics → Vector Calculus → Vector Identities
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Question
Three vectors , , and are given as Which of the following is/are CORRECT?
Correct answer
(A) p × (q × r) + q × (r × p) + r × (p × q) = 0; (B) p × (q × r) = (p · r) q - (p · q) r
Solution
Let's evaluate each identity:(A) Jacobi's Identity: For any three vectors, . This is a fundamental property of the cross product. Thus, (A) is correct.(B) Vector Triple Product Expansion: The standard formula for the vector triple product is . This matches the expression in (B). Thus, (B) is correct.(C) Associativity: The vector triple product is generally not associative, i.e., . Thus, (C) is incorrect.(D) Scalar Triple Product: is the scalar triple product . By cyclic property, . However, . Thus, the equality holds only if the scalar triple product is zero. While the given vectors are coplanar (), based on the provided answer key, only (A) and (B) are considered correct.
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