2-4: THE COORDINATE PLANE

2-4: The Coordinate Plane  C OORDINATE P LANE : A grid used to represent placement in two dimensions (x and y). Also called a C ARTESIAN P LANE. Vertical number line is called the y-axis Horizontal number line is called the x-axis The point of intersection of the two axis is called the origin

2-4: The Coordinate Plane  The Coordinate plane is broken up into four quadrants. They start in the upper- right and count counter-clockwise. Quad 1Quad 2 Quad 4 Quad 3

2-4: The Coordinate Plane  O RDERED P AIR : A point on the coordinate plane, consisting of an x-coordinate and a y-coordinate.

2-4: The Coordinate Plane  The figure below shows the graph of the ordered pair (4, 3). The first part, 4, is called the x-coordinate. It tells how many points to the left or right the point lies. (4, 3)

2-4: The Coordinate Plane  The second part, 3, is called the y-coordinate. It tells how many points up or down the point lies. (4, 3)

2-4: The Coordinate Plane  Example: Graph point A at (2, -3)  Identify the coordinates at B and C.  A (2,-3) B C B is at (-2, 5); C is at (0, -2)

2-4: The Coordinate Plane  Horizontal and vertical lines have special characteristics.  If a vertical line passes through (3, 4), then it contains all the points where x = 3.  If a horizontal line passes through (-4, -2), then it contains all the points where y = -2.  T HEOREM 2-4: If a and b are real numbers, a vertical line contains all points (x, y) such that x = a, and a horizontal line contains all points (x, y) such that y = b.

2-4: The Coordinate Plane  T HEOREM 2-4: If a and b are real numbers, a vertical line contains all points (x, y) such that x = a, and a horizontal line contains all points (x, y) such that y = b.  What???  Vertical lines are always written as x = #  Horizontal lines are always written as y = #  How am I supposed to remember that?  Take a v (for vertical), and turn it upside-down  Take a h (for horizontal), and turn it upside down vh

2-4: The Coordinate Plane  Assignment  Worksheet #2-4  Tomorrow  Quiz on Sections 2-1 through 2-4  Next Week  Monday: 2-5 (Midpoints)  Tuesday: (Keystone Review-ish)  Wednesday: Chapter 2 Preview  Thursday: Chapter 2 Review  Friday: Chapter 2 Test