6.2 Functions
Special relations : A and B are two nonempty sets. If each element of set the A is associated with exactly one element of set B, then this association is called a function from set A to set B.
Note :
Set A is the domain
Set B is the codomain
All the elements of set B need not have association
The element of set B which are associated is the set "range" of the function. Thus the range is a subset of codomain.
For example, { ( 2, 9 ) , ( 3, 13 ) } is a function { ( 2, 5 ), ( 3, 9 ) } is not a function
The element y Î B such that the function say 'f ' associates to the element x Î A is denoted by f ( x ) i.e. y = f ( x ) and y is called the 'f ' image of x or value of 'f ' at x. The element x is also called preimage of y. Every element of A has a unique image but each element of B need not have an image of an element in A. There can be more than one element of A which has the same image in B.
We denote the range of f : A ® B by f (A) Thus f ( A ) = { f ( x )  x Î A } Þ f ( A ) Î B.
The domain variable is often referred as the independent variable and the range variable is referred to as the dependent variable.
Methods of representing a function
An arrow diagram can be used.
For example if f : x ® 3 x, x Î { 2, 3, 4 } then f can be shown as

Index
6.1 Relations
6.2 Functions 6.3 Variation
Chapter 7
