411 REFERENCE · Wikibooks
Geometry Course/Polygon/Triangle
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Triangle
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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 , ,
The sum of Three angles
Similar and Congruent Triangles
Similar 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.
Properties
/Perimeter/
/Area/
Special Types of Triangle
/Right Triangle/
/Isosceles Triangle/
/Equilateral Triangle/
/Scalene Triangle/