Equivalence - Reflexive, Symmetric, and Transitive Properties
What guarantees that a relationship is an Equivalence Relationship ?
The following three properties are true for every equivalence relationship:
• Reflexive Property
• Symmetric Property
• Transitive Property
All three properties should be considered together.
For example, all three properties must be true for the equal (=), congruent (
), or similarity (
) sign to be valid in a mathematical relationship such as a function or an equation.
Reflexive Property: (a=a)
a
is equivalent to a
("a" equals "a")
Examples of reflexivity:
2 = 2
x = x
(numbers are listed in
exactly the same order)
5+4 = 5+4
X+2 = X+2
The property of reflexivity may seem ridiculously obvious. However, it is used extensively in proofs.
For example, the property of reflexivity can be used to prove that the following two triangles are congruent.
Both triangles have a common side: AC
Symmetric Property: (if a=b, then b=a)
The Symmetric and Commutative Property are similar.
a = b
is equivalent to b = a
Examples of the Symmetric Property:
(numbers are listed in
reverse order - a reflection)
5+4
=
4+5
X+2
=
2+X
This property is often used to teach elementary school children how numbers work.
For example:
Young children are taught that the numbers can be rewritten as follows:
Young children are taught that the numbers can be rewritten as follows:
Transitive Property: (if a=b and b=c, then a=c)
The Transitive Property illustrates how logic and deductive reasoning are used in mathematics. The Transitive Property shows how to draw conclusions from the information available.
The logic provided by the Transitive Property can be summarized as follows: if one item is equal to a second item, and the second item is equal to a third item, then the first item is also equal to the third item.
For example, if "Kevin is the doctor for my family" and "the doctor for my family is my cousin", then the transitive property shows that "Kevin is my cousin".
An example of how this principle can be applied to mathematics is:
.5 = 1/2
1/2 = 2/4
Therefore,
.5 = 2/4
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Reflexive, Symmetric, and Transitive Properties
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