Types of triangles

1 Star2 Stars3 Stars4 Stars5 Stars (No Ratings Yet)

Triangles can be classified by their sides or by their angles. According to these, we can assert that there are basically six different types of triangles: equilateral triangle, isosceles triangle, scalene triangle, right triangle, acute triangle, and obtuse triangle.

By Side

    Drawing of the equilateral triangle with its sides and interior angles

  • Equilateral Triangle: All three sides are equal. Therefore, its three angles are also equal. That is to say:
    Equilateral Triangle Side and Angle Ratio Formula

    Since all angles are equal and add up to 180° (why do angles add up to 180°?), they are all 60° α=β=γ=60°.

  • Dibujo del triángulo isósceles con sus lados y ángulos interiores

  • Isosceles Triangle: It has two equal sides. Hence, it also has two equal angles.
    Isosceles Triangle Side and Angle Ratio Formula

    As we see in the image above, the unequal angle β is the one formed by the two equal sides (a and c).

  • Dibujo del triángulo escaleno con sus lados y ángulos interiores

  • Scalene Triangle: All three sides are unequal, so their three angles are different too from each other. Therefore, we have that:
    Scalene Triangle Side and Angle Ratio Formula

By Angle

  • Right Triangle: It has one angle equal to 90 degrees. The other two are acute angles, i.e. they measure less than 90 degrees.
  • Oblique Triangle: It hasn’t any angle measuring 90 degrees. Oblique triangles can be classificated in:
    • Acute Triangle: all three angles are acute, that is, its angles measure less than 90°.
    • Obtuse Triangle: One of its angles is greater than 90°. The other two are acute (less than 90°).
Drawing of triangle types according to their angles

Summary: Types of Triangles

The table below shows the different types of triangles based on sides and angles:

Tabla de los tipos de triángulo según sus ángulos y lados

AUTHOR: Bernat Requena Serra

YEAR: 2020


Leave a Reply

Your email address will not be published. Required fields are marked *