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Let A be the set of all lines in xy-plane and let R be relation in A , defind by `R={(L_(1),L_(2)):L_(1)||L_(2)}.` show that R is an equivalence relation in A. Find the set of all lines related to the line ` Y=3x+5.` |
Answer» the given relation satisfies the following properties : (i) reflexivituy Let L be an arbitrary line in A then , `L||Limplies (L,L)in R AALin A.` thus ,R is reflexive . (ii) Symmetry Let `L_(1),L_(2) in A ` such that `(L_(1),L_(2) ) in R.`then , `(L_(1),L_(2))in Rimplies L_(1)||L_(2)` `implies L_(2)||L_(1)` `implies (L_(2),L_(1))in R.` `therefore ` R is symmetric . (iii) transitivity `Let L_(1),L_(2),L_(3) in A ` such that `(L_(1),L_(2)) in R and (L_(2),L_(3))in R.` then ,`(L_(1),L_(2))in R and (L_(2),L_(3))in R` `implies L_(1)||L_(2)and L_(2)||L_(3))` `implies L_(1)||L_(3)` `implies (L_(1),L_(3))in R.` `therefore`R is transitive. thus R is reflexive symmetric and transitive . hence ,R is an equivalence relation . the family of lines parallel to the line `y=3x+5` is given by `y=3x+k,` which k is real . |
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