Geometry Course/Polygon/Triangle

Triangle

 * Triangle_rectangle_amb_altura_-_Right-angled_triangle_with_height.svg

A triangle is a two dimensional polygon that has three sides and three angles with the total sum of the angles equal to 180o
 * Three Points A, B, C
 * Three sides AB, BC, CA
 * Three angles $$\angle A$$, $$ \angle B$$ , $$\angle C $$
 * The sum of Three angles $$\angle A + \angle B + \angle C = 180^o$$

Congruent Triangles
Two Triangles are equal or congruent when
 * Two triangles have three sides are equal . Side by Side by Side (SSS) 
 * Two triangles have two sides and angle in between the sides are equal . Side Angle Side(SAS) 
 * Two triangles have two angles and the side in between the angles are equal . Angle Side Angle (ASA) 

Note that there is no AAA congruence(Angle-Angle-Angle), because then the sides can be different , making it unequal. It can be similar however.

If you were to transpose one congruent triangle with the other, they would superimpose exactly.

Properties

 * 1) /Perimeter/
 * 2) /Area/

Special Types of Triangle

 * 1) /Right Triangle/
 * 2) /Isosceles Triangle/
 * 3) /Equilateral Triangle/
 * 4) /Scalene Triangle/