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21/05_Triangles


I have decided to write a specific post about the interesting properties of the triangle, the different types we can find and some examples we can find in the real world.

The triangle is a geometric figure of three sides that create three angles between them. Let’s summarise. The different elements of the triangle are:

  • Vertices: They are points where two or more line segments meet. Corners.
  • Sides: they are the line segments that create this closed figure.
  • Angles: is the space (usually measured in degrees) between two intersecting lines where they meet.
We are going to see it better in an image:


 

Fun fact! The three angles always add to 180º, for this reason, we consider triangles as very special figures.

There are different ways to classify triangles. Let’s see them:

By the measure of the segments:

  • Equilateral: three equal sides. Angles are consequently equal, always 60º.
  • Isosceles: two equal sides with two equal angle
  • Scalene: there are not neither equal sides nor equal angles.

 

                                                                               Illustration 1. Types of triangles. 
 
As Math is fun shows us, there are some interesting tips to remember them:

Alphabetically they go 3, 2, none:

  • Equilateral: "equal"-lateral (lateral means side) so they have all equal sides
  • Isosceles: means "equal legs", and we have two legs, right?
  •   Also iSOSceles has two equal "Sides" joined by an "Odd" side.
  • Scalene: means "uneven" or "odd", so no equal sides.

By the measure of their angles:


·       Acute angle: all angles are less than 90º.
·       Right angle: it has a right angle (90º).
·      Obtuse angle: one angle is more than 90º and the other two, less than 90º. 








Illustration 2. Types of angles on the basis of angles.   


Name the following angles in base to its classification according to their sides and also their angles:




We would like to finish this post with a challenging task that will make you think. Would you be able to do it? 

 

Buser, P. y Costa, A. (2012). Curso de geometría básica. Madrid: Sanz y Torres.

Definition of vertex. (n.d.). In Math is fun. Retrieved from: https://www.mathsisfun.com/definitions/vertex.html

García, J. (2013), Resumen teórico Matemáticas y Ciencias. Lima: Rodó.

Guedj, D. (2002). El teorema del loro: Novela para aprender matemáticas. Barcelona: Editorial Anagrama.

Polanía Sagra, C. y Sánchez Suleta, C. (2007). Un acercamiento al pensamiento geométrico. Colombia: Universidad de Medellín.

Triángulo. (2019).  In Wikipedia. Retreived from  https://es.wikipedia.org/wiki/Tri%C3%A1ngulo#Clasificaci%C3%B3n_seg%C3%BAn_los_lados_y_los_%C3%A1ngulos_del_tri%C3%A1ngulo

Triangle. (n.d.). In Math is fun. Retrieved from https://www.mathsisfun.com/triangle.html
 

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