Scratch LESSON #4 Coordinate Plane


Purpose: This lesson introduces the coordinate plane.Essential Question: How do we put the a sprite in a specific location on the coordinate plane?


The Coordinate Plane:The connection between geometry and algebra is the coordinate grid. A grid can be shown on a plane. An ordered pair will represent a point in the plane. A plane has two dimensions, which is why points are represented by two values.
The first coordinate is called the abscissa and moves left or right. The second coordinate is called the ordinate and moves up or down. It is important to use the correct order (abscissa, ordinate). The ordered pair (0, 0) is called the origin. In Scratch, the cat’s home location is the origin.
In this lesson, the canvas was changed to a grid by selecting the xy-grid backdrop.
New Command go_to.pngMoves the sprite to the (x, y) point in the coordinate plane.The default values are the origin.
Figure 1 shows the code to draw a rectangle.CoordGridRectangleCode.pngFigure 2 shows a grid in the graphics window. Segments were drawn from the point (200, 150) to points in each corner of the grid in a counter clockwise direction. Recall that the ordered pair moves horizontally the amount designated by the first coordinate (x), and moves vertically the amount designated by the second coordinate (y).CoordGridRectangleGraphic.png
New Command

glide_to.png
Moves the sprite slowly from a location to a new point
This example uses a 3 second time span.
Figure 3 shows the code to draw green line segments from the origin to five different points in the coordinate plane.

CoordGridVectorsCode.png
Figure 4. Graphic for this set of code. These segments are called vectors in a later lesson.
CoordGridVectorsGraphic.png

TASK 1: Experiment with the go to and glide to commands by predicting where the sprite will be in the coordinate plane.

TASK 2: Experiment moving the sprite with only the abscissa and ordinate commands.

CoordGridAbscissaCommands.png

CoordGridOrdinateCommands.png
TASK 3: What is a quadrant in the coordinate plane?