Math 6A ( Periods 2 & 5)

The Coordinate Plane 6-5

The Coordinate Plane is formed by the intersection of a horizontal number line ( x-axis) and a vertical number line ( y-axis)
They intersect at the origin (0,0) and the ORIGIN separates the Coordinate Plane into FOUR regions called QUADRANTS


A PAIR of numbers whose ORDER is important is called an   ordered pair
(ordered, pair) (x, y)

(2,3) is not the same as (3,2)

The two perpendicular lines are called axes.
The x-axis deals with the 1st number of the ordered pair and the y-axis deals with the 2nd number of the ordered pair.
The AXES meet at a point called the Origin (0,0)
The plane is called the coordinate plane

There are 4 quadrants, You MUST use Roman Numerals to name them!!
Quadrant I ---> both the x and y coordinates are positive
(x,y) (+,+)

Quadrant II --> the x coordinate is negative but the y is positive
(-x,y) (-,+)

Quadrant III -->. both the x and y coordinates are negative
(-x,-y) (-,-)

Quadrant IV --> the x coordinate is positive but the y coordinate is negative
(x,-y) (+,-)

Reflect a point in the x-axis
Use the same x-coordinate and take then opposite of the y- coordinate

Reflect a point in the y-axis
Use the same y-coordinate and take then opposite of the x- coordinate

Reflect a point in both axes:
1) x followed by y
First follow the steps above so for (2,1) reflect in x followed by y means
(2,1)--> (2, -1), then --> (-2,-1)  What do you notice? Both coordinates are now the opposites of what they started as!