1. The coordinate plane works just like a number line.
Points on a Plane
Coordinate Plane
Coordinates are written as an ordered pair in the form (x,y). y
Quadrant II
Quadrant I 7 6 5 4 3 2 1 B
(-4, 6)
The x-coordinate is also called the abscissa and the y-coordinate is also called the ordinate. A
(2, 3) x -1 -2 -3 -4 -5 -6 -7
The coordinate plane works just like a number line. D
(5, -4) C
(-7, -5)
Quadrant III
Quadrant IV

2. Graphing Polygons
A polygon is a closed figure whose sides are line segments. The endpoints of the sides are called vertices.
A polygon can be represented on a coordinate plane by locating its vertices and drawing the sides by connecting the vertices in order. y
Graph rectangle ABCD whose vertices are: 8 6 4 2 -2 -4 -6 -8 B
(-8, 6) A
(8, 6)
A (8, 6), B (-8, 6), C (-8, -6), D (8, -6)
We can find the dimensions of the rectangle by counting the number of units between the points. x
Find the length by subtracting the x-coordinates.
(8) - (-8) = 16
Find the width by subtracting the y-coordinates.
(6) - (-6) = 12 C
(-8, -6) D
(8, -6)

3. Area on the Coordinate Plane
Let’s take another look at that rectangle again.
Graph rectangle ABCD whose vertices are:
A (8, 6), B (-8, 6), C (-8, -6), D (8, -6)
We already found the length and the width of the rectangle. Now we can use those measurements to find the area of the rectangle. y 8 6 4 2 -2 -4 -6 -8 B
(-8, 6) A
(8, 6)
The length = 16
The width = 12 x C
(-8, -6) D
(8, -6)

4. Triangle Area on the Coordinate Plane
Graph the following points: A(4, 1), B(1, 5), C(-2, 1). Then connect the vertices and find the area of the polygon. y 9 8 7 6 5 4 3 2 1 -1 B
(1, 5) A
(4, 1) C
(-2, 1) D
(1, 1)
Asi De
Facil x

5. More Area Examples graph each polygon identify the polygon
A (-3, -2), B (2, -2), C (2, 2), D (-3, 2)
graph each polygon
identify the polygon
(c) find the area.
Example 1
(b)
Rectangle
(c)
length = 5
width = 4 y C
(0, 7)
(a)
(a)
(a)
Example b 5 4 3 2 1 -1 -2 -3 -4 -5 5 4 3 2 1 -1 -2 -3 -4 -5 5 4 3 2 1 -1 -2 -3 -4 -5
A (-4, 2), B (0, 2), C (0, 7)
(b)
Right Triangle D
(-1, 3) C
(3, 3) D
(-3, -2)
(c)
base = 4
height = 5 C
(2, 2) A
(-4, 2) B
(0, 2) x
Example 3 A
(-1, -1) B
(3, -1)
A (-1, -1), B (3, -1),
C (3, 3), D (-1, 3) A
(-3, -2) B
(2, -2)
(b)
Square
(c)
side = 4

6. Graphing Homework Page 80 - 81 3 -19, 24, 25, 27
Do all problems on graph paper. Do all of number 3 on one grid, 4 – 15 on one grid, and 24, 25, and 27 each on separate grids