Triangle_Joseph

 

A triangle is a plane figure with three straight sides and three angles.  

 

Triangles are classified in 2 ways :

1) By the number of equal sides they have:

   • scalene - all 3 sides have different lengths

   • isosceles - 2 sides have equal lengths

   • equilateral - all 3 sides are equal

2) By the types of angles they have:

   • acute triangle - all 3 angles are acute (less than 90°)

   • right triangle - has one right angle (a right angle = 90°)

    • obtuse triangle - has one obtuse angle (an obtuse angle is greater than 90° and less than 180°).

 

There are 8 possible types of triangles :

1.    Acute scalene (a triangle which angles are smaller than 90º and have 3 different sides

2.    Right scalene (a triangle which have an angle of 90º and has 3 different sides)

3.    Obtuse scalene (a triangle which have an angle more than 90º but less than 180º and has 3 different sides)

4.    Acute isosceles (a triangle which angles are smaller than 90º and has 2 different sides)

5.    Right isosceles (a triangle which have an angle of 90º and has 2 different sides)

6.    Obtuse isosceles (a triangle which have  an angle more than 90º but less than 180º and has 2 different sides)

7.    Equilateral triangle (all sides are equal and each angle are 60º)

8.    Oblique triangle (any triangle that is not a right triangle).  It could be an acute triangle (all threee angles of the triangle are less than right angles) or it could be an obtuse triangle (one of the three angles is greater than a right angle)