A triangle is a polygon with three sides. The various types of triangles are named according to the types of sides and angles that make them up. Remember that the three internal angles in a triangle always add to 180°.

Types of Triangles Based on Sides and Angles


  • Equilateral or Equiangular triangle :
    All three sides are equal.
    All three angles are equal and 60°.
    .

  • Isosceles triangle:
    Two sides of the triangle are equal.
    The two angles at the base are equal.


  • Scalene triangle:
    None of the sides or angles are equal.


Types of Triangles Based on Angles



  • Acute Triangle:
    The angles are all acute (less than 90°).


  • Right Triangle:
    One of the angles is 90°.


  • Obtuse Triangle:
    One of the angles is obtuse (between 90° and 180°.


    Combinations

    Match the description on the left with the picture on the right by entering the description number in the blank below each picture; when done, scroll down to check your answers by holding your mouse cursor over the grey box.

    1. Isosceles Right Triangle:

    A right triangle in which two sides and two base angles are equal.     		 


    2. Acute Scalene Triangle:

    A triangle that has three unequal sides and three acute angles.     		 




    3. Obtuse Isosceles Triangle:

    A triangle in which two sides are equal and one angle is an obtuse angle.     		 





    4. Obtuse Scalene Triangle:

    A triangle with an obtuse angle and sides of different lengths.     		 




                 



    Resources


    Content, HTML, graphics & design by Bill Willis 2024