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Jul11

Geometric Figures and Straight Lines

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Straight lines are key to recognizing shapes that we often see in the real world: Geometric figures.

In today’s post we will classify geometric figures formed from straight lines and think about where we can find them.

We’ll start with the simplest:

Two Straight Linesgeometric figuresCan you make a figure with two straight lines?

geometric figuresWell, of course you can! However, we do not call this figure a geometrical figure.  In order to be a geometrical figure, it must be “closed.”   That is to say, if we put a ball inside the figure, it could not escape.  In the figure we have made, the ball could escape!

geometric figuresIf you try to move the two lines, you will see that in no way can it be closed. You could take two straight objects, for example two chopsticks, and try.

Basic Geometric Figures

Let’s now try it with three straight lines
geometric figuresThat’s it! Now you can make a figure that the ball cannot escape.

geometric figuresEach of the straight lines we used now act as a part of the figure.

We will call a each straight line a side of the figure. So, this figure has three sides and is called a triangle. When we say “triangle” we are either referring to how to arrange the three lines or the enclosing space.

geometric figuresCan you imagine where we can find triangles around us? I found some in Smartick, let’s see if you recognize them!

geometric figures4-Sided Geometric Figures

Let’s see what we can do with 4 straight lines

geometric figures

We could make, for example,

geometric figuresWe call these figures quadrilaterals. There are some very special quadrilaterals that have pairs of parallel sides. That is, there are two sides which are parallel to each other, and the other two are also. In addition, the sides that are parallel are equal.  How could we make these? We get two equal sides and put them parallel to each other:

geometric figures

How can we place the other two sides so that they are also parallel? That’s it! Simply by joining

geometric figuresAt this point we have three possibilities:

  • All the sides are equal. Creating a diamond

geometric figures

Where can you find diamonds?

geometric figuresI found two!

  • If the four angles of the figure are right angles, then we have created a rectangle

geometric figuresWe can find many rectangles around us … I’m sure that you can think of many!

geometric figures
  • If we create a geometric shapes that meets both of the above conditions and also has all equal sides and four right angles it is a square.
geometric figuresGeometric Figures With More Than 4 Sides

We can keep adding all the lines we want to create different shapes with different numbers of sides. They are especially important when they have equal sides. For example, the following would be the pentagon (5-sided)
straight lines
We can find them, for example, in the drawing of soccer balls
straight lines

And then we have the hexagon (6-sided).
straight linesWe can find them … in beehives! How do bees know how to make such perfect geometric shapes?

geometric figuresAnd then heptagons, octagons, enneagon, nonagons … any missing? Of course! What can we do with curved lines? With curved lines it does not make sense to classify them because they vary so much more … but I can tell you that there is a very, very important curved figure that I am sure you already know of… the circle!

straight linesWe get a circle when we keep the distance to a point. For example, with a compass, we set a point with a needle. Then, keeping the opening, we draw the circle with a pencil. You can find a lot of circles around you, on the wheels of your car or a tennis ball.
geometric figuresIf you want, you can continue learning elemmentary math with Smartick!                                                                          

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