There we learned the four variations of a proposition: the obverse (the proposition itself), the inverse, the converse, and the contrapositive. Obverse: If P then Q. Inverse: If not P then not Q. Converse: If Q then P. Contrapositive: If not Q then not P. If the obverse is true, then the contrapositive is also true. The inverse and converse may not be. Mathematical reasoning is a deductive process and the basic entity to it is a statement. The statements in reasoning can be compound i.e. they can be composed of two or more than two statements together.
Venn Diagrams are used to graphically show the grouping of elements in sets, representing each set in a circle or an oval.