# Lesson 6 The Coordinate Plane

Coordinate Plane
y
Axes (plural of axis)
0 x-axis
0 y-axis
x
Coordinate Plane
y
Origin
x
Coordinate Plane
y
II
I
III
IV
x
Coordinates
Plot and label the points:
0 A(4,7)
0 B(-3,5)
0 C(4,-7)
0 D(-6,-3)
each point is graphed.
Coordinates
State the coordinates:
0A
0B
0C
0D
0E
0F
(5,2)
(-8,-5)
(-3,5)
(4,-7)
(0,4)
(-7,0)
C
E
A
F
B
D
Distance in the coordinate plane
Kayleigh walks to a friend’s house by traveling 5 blocks
west and then 12 blocks north. She returns home later
by cutting diagonally through her neighbors’ yards.
What distance did she travel on her voyage home?
13
12
5
a 2  b2  c 2
52  122  c 2
25  144  c 2
169  c 2
169  c 2
13  c
Distance formula
0 The distance between two points x1 , y1  and x2 , y2  on
the coordinate plane (graph) can be found using the
formula:
d
x2  x1    y2  y1 
2
2
http://www.bsin.k12.nm.us/schools/BHS/math/joinmath/geometry/GEO1_3.pps#257,4,Slide 4
Practice
Find the distance between R(–2, –6) and S(6, –2) to the nearest tenth.
d=
(x2 – x1)2 + (y2 – y1)2
d=
(6 – (–2))2 + (–2 – (–6))2
d=
82 + (–8)2
d=
64 + 64 =
128
To the nearest tenth, RS = 11.3.
Midpoint Formula
In the coordinate plane, the coordinates of the midpoint
of a segment whose endpoints have coordinates ( x1 , y1 )
and ( x2 , y2 ) are  x1  x2 , y1  y2  .


2
2


Example: Find the midpoint between (-2, 5) and (6, 4)
x1 y1
M=
2  6 , 5  4 
 2
2 
M=
4 , 9  = 2, 9 
2 2   2 
x2 y2
Practice
AB has endpoints (8, 9) and (–6, –3). Find the coordinates of its midpoint M.
(
x1 + x2
2
8 + (–6)
2
=
=1
2
2
,
y1 + y2
2
)
9 + (–3)
6
=
=3
2
2
The coordinates of midpoint M are (1, 3).
Homework
The Coordinate Plane in
Student Practice Packet
(Page 7, #1-13)