Plane Figures: Straight Line in a Horizontal Plane

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  • Box of sticks
  • Supplies
  • Board



  1. The directress tacks a stick onto the board and identifies the board as a plane; a straight flat surface that continues in all directions infinitely.
  2. Imagine that this stick is a straight line that goes on infinitely in both directions.
  3. Hold the plane vertically and ask the child to identify the position of the line as the plane is rotated: 1800...horizontal..oblique...oblique...vertical...oblique...etc.
  4. Hold the plane obliquely.
  5. The plane in space could be in any position, but to facilitate your work, the plane will always be horizontal, like the surface of your work table.
  6. Tack on two other sticks so that the three positions are represented: -, /, |.
  7. If these three lines were considered in space they would all be horizontal.
  8. Hold the plane at eye level to show this.
  9. Let's consider them on the plane surface.
  10. When a straight line follows the direction of the viewer's body, it's vertical.
  11. When a straight line doesn't form a cross or follow the same direction of the viewer's body, it's oblique.

Control Of Error

Points Of Interest



1. Leave only one stick on the board. As the plane is rotated (always horizontally) the child identifies the position of the line.
2. To understand that these positions are relative to the viewer, seat two children so that a right angle is formed between their bodies and the plane. As the plane is rotated, the children simultaneously identify the line as they view it.
3. The child draws the lines on the blackboard. The criteria hold true even if the plane is vertical (or oblique) like the blackboard.