# Geometry Course/Polygon/Triangle

## Triangle

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 ${\displaystyle \angle A}$ , ${\displaystyle \angle B}$ , ${\displaystyle \angle C}$
The sum of Three angles ${\displaystyle \angle A+\angle B+\angle C=180^{o}}$

## Similar and Congruent Triangles

### 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.