csec mathematics review - introduction to functions & relations
TRANSCRIPT
Topics To Be Covered
• Define What is a Func/on – Show Simple Examples of Func<ons – Explain How Func<on Nota<on Works
• Define What is a Rela/on – Define The Terms Domain and Range – Learn How To Draw Mapping Diagrams – Learn The Different Types of Rela<ons – Lean How To Test For Func<ons
What is a Func<on
• A func<on in a typical sense is just a machine with a specific rule that produces a single output.
Example
• Consider the following machine which is used to convert our local Barbadian currency into US Dollars.
OR y = 0.5 x
(5)BBD
Currency Converter
(2.5)USD
Output Rule Input
Example Con<nued The func<on given is an example of a Linear Func/on. We will discuss the graphs of func<ons later but here is the graph of our currency converter func<on.
Func<on Nota<on
• There is a more appropriate way that we use in calculus to represent a func<on in wri<ng and that is:
f(x) = y
The input (variable) is listed in brackets
Output Name of Func<on
Rela<ons The topic of func<ons is in fact in sub-‐topic under him much broader subject In mathema<cs called Rela/ons.
Defini<on: A rela<on is a set of ordered pairs.
What it is an ordered pair?
Well let us use this func<on as an example:
f(x) = x2 + 1
Let us list our inputs from 1 to 5 and calculate their corresponding outputs: Now we can pair our inputs with our outputs in an orderly fashion like this:
Formal Defini<on of a Func<on
• A func<on a special rela<on in which each element x in the Domain is paired using a rule, with exactly one and only one element f(x) in the Range.
• There are two types of rela<ons that sa<sfy this criteria and they are called one-‐to-‐one and many-‐to-‐one rela<ons.
• A one-‐to-‐many rela<on is NOT a func<on.
Example of One-‐To-‐One Func<on Consider the rela<on f: x → 2x + 5 given that the domain is Find the corresponding range values and hence draw a mapping diagram to represent the rela<on.
0, 1, 2, 3
One-‐To-‐One Func<ons Con<nued
A func<on from set A to set B is said to be an One-‐To-‐One (injec<ve) func<on if no two or more elements of set A have the same elements mapped or imaged in set B.
Many-‐To-‐One Func<ons Con<nued
A func<on from set A to set B is said to be a many-‐to-‐one func<on if two or more elements in set A processed through the func<on produces the same output or same element in set B.
One-‐To-‐Many is Not A Func<on Consider the inverse of func<on f(x) = x2 in which we generate by exchanging the values for the domain and range. The inverse func<on follows the rule:
f ’(x) = ± √x
A Visual Test For Func<ons
We can use a very simple test called the Ver/cal Line Test to determine whether the Graph of A Rela/on in indeed a func<on or not. • Defini<on: – Given a curve drawn in the coordinate plane. Then this curve is a graph of a func<on if and only if no ver<cal line can be made to intersect the curve at more than one point.