You are in Geometry/2D (plan) section

Welcome in our Geometry/2D (plan) section. As we have seen in the previous section in the 1D-world we can move back and forth in the dimension (the line) and only in the direction of that dimension (the direction has been fixed, first). If we change, for instance, the direction of the line: we generate a 2D-world.

What's a 2D-world? A 2D-world is a world with two (2) dimensions. A 2D-world is a flat world. For instance a flat world can be represented by a plan.

Examples:

A sheet of your notebook is a plan. A TV screen or the screen of your computer is a plan. In a plan we have the freedom to move back and forth along two main directions. When we draw a picture on a sheet we move our pen following a 2D-world, i.e. a flat world or a plan.

Other examples:

- a window;

- a CD (compact disk);

- area of a table;

Note: in a plan the freedom of your movement is limited to the plan. For instance, if you want to draw or write in a 2D-world (like on a sheet of your notebook) your pen must stay on the sheet. What happen if the pen leave the sheet? The pen is moving in a 3D-world. This is our world. To see more on a 3D-world, we invite you to see the next section (3D-space).

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