વિધાન: "જો ચતુષ્કોણ $ABCD$ સમબાજુ ચતુષ્કોણ હોય,તો તેની સામસામેની બાજુઓ સમાંતર હોય છે" માટે,તેનું પ્રતિ-વિધાન (contrapositive) અને પ્રતીપ-વિધાન (converse) અનુક્રમે નીચે મુજબ છે:

• A
  $i$. If opposite sides of a quadrilateral $ABCD$ are not parallel,then quadrilateral $ABCD$ is not a rhombus. $ii$. If opposite sides of a quadrilateral $ABCD$ are parallel,then quadrilateral $ABCD$ is a rhombus.
• B
  $i$. If opposite sides of a quadrilateral $ABCD$ are not parallel,then quadrilateral $ABCD$ is not a rhombus. $ii$. If opposite sides of a quadrilateral $ABCD$ are parallel,then quadrilateral $ABCD$ is a rhombus.
• C
  $i$. If opposite sides of a quadrilateral $ABCD$ are not parallel,then quadrilateral $ABCD$ is not a rhombus. $ii$. If opposite sides of a quadrilateral $ABCD$ are parallel,then quadrilateral $ABCD$ is a rhombus.
• D
  $i$. If opposite sides of a quadrilateral $ABCD$ are parallel,then quadrilateral $ABCD$ is not a rhombus. $ii$. If opposite sides of a quadrilateral $ABCD$ are not parallel,then quadrilateral $ABCD$ is a rhombus.