A triangle is one of the basic shapes of geometry: a polygon with three corners or vertices and three sides or edges which are line segments.
The sum of all the internal angles in the triangle is 180º.
How to label a triangle
- The vertices of the triangle are named with capital letters (A, B, C)
- The sides of the triangle are named with the letter of its opposite vertex (a, b, c)
- The angles of the triangle are named with the letter of the vertex and angle symbol (^).
Types of triangles
Triangles are classified two ways:
For their SIDES:
Three equal sides and angles.
Two equal sides and angles.
No equal sides or angles.
For their INTERNAL ANGLES
All their angles are ACUTE.
One RIGHT ANGLE.
In right triangles, the sides that form the right angle are called LEGS and the side that faces them is called HYPOTENUSE.
One OBTUSE angle.