Investigation 7: The Coordinate Plane
Investigation 7: The Coordinate Plane is a Grade 6 math investigation in Saxon Math, Course 1 that introduces students to the four-quadrant coordinate system. Students learn to plot ordered pairs (x, y) where the x-value indicates horizontal position and y indicates vertical position. The origin (0,0) is the intersection of the x-axis and y-axis. Quadrant I has positive x and y; Quadrant II negative x, positive y; Quadrant III both negative; Quadrant IV positive x, negative y. Students practice plotting, identifying, and describing points to build the spatial reasoning needed for graphing linear equations in pre-algebra.
Key Concepts
New Concept A coordinate plane is a grid formed by two perpendicular number lines, the x axis (horizontal) and y axis (vertical). The numbers that tell the location of a point are the coordinates , written as an ordered pair like $(x, y)$. What’s next This is just the foundation. Soon, you'll use this system in worked examples to plot points, find coordinates, and analyze geometric shapes like rectangles.
Common Questions
What is the coordinate plane?
A flat surface defined by a horizontal x-axis and vertical y-axis that intersect at the origin (0,0). Every point on the plane is identified by an ordered pair (x, y).
How do you plot an ordered pair on a coordinate plane?
Start at the origin (0,0). Move left or right along the x-axis by the x-value, then up or down along the y-axis by the y-value. Mark the point where you land.
What are the four quadrants of the coordinate plane?
Quadrant I: positive x and y (upper right). Quadrant II: negative x, positive y (upper left). Quadrant III: both negative (lower left). Quadrant IV: positive x, negative y (lower right).
What is the origin on a coordinate plane?
The origin is the point (0, 0) where the x-axis and y-axis cross. It is the starting reference point for all coordinates.
Why is the x-value always written before the y-value in an ordered pair?
By convention, the horizontal position (x) is listed first and the vertical position (y) second. The order matters: (3, 5) and (5, 3) are different points.