In grades 9 and 10 you learned about linear and quadratic relations. In this course you will broaden your understanding by learning about a group of relations called functions. You will also expand your mathematical vocabulary to include new ways to describe relations, including stating the domain and range, which describe where, on the Cartesian plane, you will see points on the graph of a relation. You will also represent relations using mapping diagrams, graphs and tables of values.
We are going to start by defining the term relation.
After watching the video, take a few minutes to answer the following questions:
- Without looking at the video again, can you recall how many ways there are to express a relation? List the ones you remember.
There are 7 ways of expressing a relation.
- List of ordered pairs
- Mapping diagram
- Table
- graph
- Equation
- Words
- Rule
- Which ways are most familiar to you?
Multiple answers are possible.
Common answer: Table, graph and equation.
- Which ways are least familiar to you?
Multiple answers are possible.
Common answer: Mapping diagram
Note
This learning activity will help you better understand the various ways of expressing relations.
- A relation is an expression that demonstrates the connection (relationship) between two variables: an independent variable (x) and a dependent variable (y).
- The expression can be in the form of a set of ordered pairs, a mapping diagram, a table of values, a graph, an equation, a description in words, or a rule.
Now let’s build up on our knowledge of relations by analyzing the examples below:
Look carefully at the two examples of relations. What is same? What is different?
Example 1 is in words and example two is a table of values. Both examples are examples of relations. In the second relation, two heights (dependent variable) are associated with a single age (independent variable). For example, heights of 152 cm and 185 cm are associated with 15 years of age.
The difference between the two relations brings us to the definition of a special type of relation called a function.
Definition
A function is a relation where each value of the independent variable corresponds to only one value of the dependent variable (no repeated values, but it’s okay for the values to be repeated).
Let’s revisit our two examples of relations.
In conclusion, a relation can be further classified as a function if there is only one value of the dependent variable for each value of the independent variable.
A function in the form of an equation can be expressed using what we call function notation.
- With function notation, we replace with , read as “ at ” or “ of ”
- means “the value of the dependent variable for a specific value of ”
- It means that we are expressing an equation as a function in terms of
- It means that
Take a minute to watch the video below to learn about the advantage of using function notation:
Now let’s re-visit example 1 and make an equation for the function, and then express it using function notation.
What steps should I take?
In example 2, Mina recorded the ages and heights of her cousins and presented the information in the form of a table on the right.
Can we express this relation using function notation?
No. The relation above is not a function, therefore it cannot be expressed using function notation.
Age | Height in centimeters |
---|---|
15 | 152 |
15 | 185 |
16 | 155 |
17 | 170 |
17 | 173 |
18 | 185 |
20 | 161 |
Domain and Range
Key features of all relations are domain and range.
- the domain is the set of all possible values of the independent variable
- the range is the set of all possible values of the dependent variable
Let’s use our two examples to practice stating the domain and range
Examples
When given a graph, a quick way of determining whether a relation is a function is by carrying out a test called the vertical line test.
You imagine drawing vertical lines anywhere on the given graph. If the relation:
- is not a function, the vertical line will pass through at least two points on the graph of the relation
- is a function, the vertical line will pass through only one point on the graph of the relation
Let’s Practice
You can also recognize whether a relation is a function, or not, given its equation.
- Linear relations with the general forms below are functions:
- Slope y-intercept form:
- Standard form: or
- Quadratic relations with the general forms below are functions:
- Standard form:
- Vertex form:
- Factored form:
- Circles with the general forms below are not functions:
- Centre at the origin:
- Centre at (a, b):
Practice Questions
Notebook
Complete the questions that follow in your Notebook. When you are done, compare your work to the solutions given. If you have errors, identify them, write about them, and do the question again below your previous set of solutions.
Self-Reflection
In this course you are an independent, self-directed learner. Consider this definition of a self-directed learner:
Definition
Self-directed learners are aware of how they learn best. They are confident and know when to ask for support. Self-directed learners set goals and make realistic plans to meet those goals. In other words, they make a commitment to their own learning and take responsibility for it.
As a self-directed learner, track your progress on the following:
Now take some time to review and reflect on the Learning goals and Success criteria in this Learning activity.
How would you rate your understanding of the concepts from this Learning activity? Check one.
Based on your assessment, do you need more review? Additional practice can be found on the Centre for Education in Mathematics and Computing website, or by searching for resources using key words from the success criteria for this learning activity.
Culminating Activity
Part of the evaluation of this course will be in the form of a culminating activity, worth 10% of your final course work.
Throughout this course, you will learn about different types of functions, transformations and domain and range. For the culminating activity, you will use this knowledge to create a logo or picture that is informative or suggests solutions to problems that are contributing to environmental issues.
This culminating activity is an opportunity for you to showcase your knowledge of different types of functions and relations as well as your knowledge of domain and range.
Remember: This culminating activity is an opportunity for you to showcase your knowledge of different types of graphs as well as your knowledge of domain and range.
- I have identified an environmental issue and created a logo to effectively represent that issue by making connections between algebraic and graphical representations of functions.
- I have created the logo on graph paper using correct mathematical form, including appropriate, clearly indicated scales.
- I have described how the logo relates to the issue that was chosen.
- I have used a minimum of four different types of functions or relations in my logo.
- I have included an equation for each function that features a minimum of three transformations to modify the parent function.
- I have described the three transformations that modified the parent function.
- I have stated the domain and range of each function, using correct mathematical language and notation.
- I have appropriately restricted the domain and/or range to support the construction of the logo.
Rubric
The teacher will assess your work using the following rubric. Before submitting your assessment, review the rubric to ensure that you are meeting the success criteria to the best of your ability.