Let I be a set of all lines in a XY plane and R be a relation in I defined as R = (I₁, I₂):I₁ is parallel to I₂. What is
The trick is using formula we get Equivalence relation. Calculation gives this directly, check steps: apply rule, substitute values, simplify to get Equivalence relation.
Ref: NCERT Mathematics Class XI — Sets, Relations and Functions
