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Let R be the relation over the set of all straight lines in a plane such that ℓ1 R ℓ2⬄ ℓ1⊥ ℓ2. Then, R isA. symmetricB. reflexiveC. transitiveD. an equivalence relation |
Answer» A. symmetric Think of line as a vector quantity: As ℓ1⊥ ℓ2; And ℓ2⊥ ℓ1 Hence R is symmetric. Also Given a relation R over straight lines such that ℓ1⊥ ℓ2 As ℓ1⊥ ℓ2: ⇒ ℓ1. ℓ2=0(DOT PRODUCT) ∵ cos θ =0 as θ =90°; ⇒ This thing is possible if ℓ1 and ℓ2 are symmetric. E.g. A= 2i-4j and B=-4i-2j ⇒ A. B=-8+8=0 |
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