If a relationship is not a function, climate it is just a subset the $A$ and also $B$ denoted together $A imes B$. Then have the right to this subset be one-to-one? can it it is in onto?
One-to-One?: also though $A imes B$ is not a function, I believe it satisfies the requirements of being one-to-one due to the fact that in $A$, $x_1 = x_2$ only as soon as $x_1 = x_1$.
You are watching: A relation that is not a function
Onto?: I want to speak yes also. The range of $A$ might be the selection of $B$. If $A imes B = (1,9), (1,8), (3,8)$, then does this satisfy the need of gift onto?
Basically what is piquing mine curiosity is if non-function relations have the right to be one-to-one or onto or if gift one-to-one and/or ~ above implies the it should be a function.
request Mar 17 "19 at 17:50
Evan KimEvan Kim
2,2081010 silver- badges2323 bronze badges
include a comment |
1 price 1
active oldest Votes
The answer right here is yes, relationships which space not attributes can likewise be defined as injective or surjective. You deserve to read an ext about the on the wikipedia page below under the section titled "Special species of binary relations," yet the interpretations are the organic ones:
A relationship $Rsubset A imes B$ is injective if for every $a,a"in A$ and $bin B$, $(a,b)in R$ and also $(a",b)in R$ means $a = a"$.
A relationship $Rsubset A imes B$ is surjective if for each $bin B$, over there is part $ain A$ such that $(a,b)in R$.
Some examples will hope clarify:
If $A = \ubraintv-jp.combf1$, a singleton through one element, and also $B = \ubraintv-jp.combf 1,ubraintv-jp.combf 2,ubraintv-jp.combf 3$, climate the relationship $R = (ubraintv-jp.combf 1,ubraintv-jp.combf 1), (ubraintv-jp.combf 1,ubraintv-jp.combf 2), (ubraintv-jp.combf 1,ubraintv-jp.combf 3)$ is both injective and also surjective, and also it is not a function.
If $A = \ubraintv-jp.combf 1,ubraintv-jp.combf 2,ubraintv-jp.combf 3$, $B = \ubraintv-jp.combf 1,ubraintv-jp.combf 2$, climate the relationship $R = (ubraintv-jp.combf 1,ubraintv-jp.combf 1), (ubraintv-jp.combf 2,ubraintv-jp.combf 1)$ is not injective, no surjective, and also it is no a function.
See more: How Big Is 1 Oz Of Cheese In Cups? How Do You Measure Cheese
If $A = Bbb R$, the set of genuine numbers, $B = Bbb R_ge 0$, the set of non-negative actual numbers, and $Rsubset A imes B$ is the relation $R=(x,x^2): xin Bbb R$, then $R$ is a surjective function, but it is not injective.