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JEE MainMathematicsSets and Relations

Let S be the set of all vectors in a two-dimensional space R ^2 . A relation R is defined on S such that for any two vectors a and b in S , a R b if and only if a b = | a || b | . Then the relation R is

Options

  1. AReflexive, symmetric and transitive
  2. BReflexive and transitive but not symmetric
  3. CSymmetric and transitive but not reflexive
  4. DReflexive and symmetric but not transitive

Correct answer

D. Reflexive and symmetric but not transitive

Step-by-step solution

For reflexivity, consider a vector a S . a a = | a |^2 = | a || a | Thus, a R a is true for all a S . The relation is reflexive. For symmetry, let a R b . a b = | a || b | b a = | b || a | Thus, b R a is true. The relation is symmetric. For transitivity, let a R b and b R c . Consider the case where b = 0 (the zero vector). For any vector a , a 0 = 0 and | a || 0 | = 0 . Thus, a R 0 is true for all a S . Let a = i and c = j . We have i R 0 and 0 R j . However, i j = 0 , while | i || j | = 1 1 = 1 . Since 0 1 , i is

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