Math 1513 Sec 1.1
1
Section
1.1
Introduction to Graphing
A coordinate system is a convenient way to visually display a
relationship between two variables.
To create a coordinate
system, we draw two lines in a plane perpendicular to each
other.
The lines intersect at the point (0,0) which is called the
origin
.
The vertical line is called the
y
axis
and the horizontal
line is called the
x
axis
.
The axes partition the plane into four
regions called
quadrants
. The quadrants are numbered using
Roman numerals starting in the upper right and moving
counterclockwise.
When plotting a point like (3, 4) in the coordinate system, the
first number indicates the point’s horizontal location along the
x
axis and the second number indicates the point’s vertical
location along the
y
axis. Thus for the point (3, 4), x = 3
and
y
= 4.
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2
Graphing Equations
Example:
Draw the graph of
3
4
12
y
x
.
Your calculator can do most of the work for you in drawing this
graph.
You just have to help it a little.
You need to rewrite the
equation so that it starts out as
y
.
For example:
4
12
3
3
4
3
3
4
12
3
4
12
4
y
x
y
x
y
x
y
x
Now we are ready to draw the graph.
Press the Y= button on your calculator and
enter the right side of the equation above
as Y1.
You could argue that the parentheses around
4/3 are not necessary.
However, it never hurts to put extra sets
of parentheses just to make sure the calculator does the
arithmetic correctly.
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 Fall '08
 staff
 Algebra, Midpoint Formula, Euclidean geometry

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