Download triangle notes - classifying

Triangle notes
October 10, 2016
Triangles!
Triangles can be classified in two different ways:
1. By their angles:
a. If every angle in a triangle is less than 900 it is acute
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b. If there is one 90o angle, it is right
30o
90o
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c. If there is one angle that is greater than 90o, it is obtuse
40o
110o
30o
*It is impossible to have more than one obtuse or 90o angle in a triangle
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Triangle notes
October 10, 2016
2. By the number of congruent sides they have.
*In geometry, congruent means equal, or exactly the same
a. If a triangle has no congruent sides, it is called scalene
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b. If a triangle has two congruent sides, it is called isosceles 6
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c. If a triangle has all three sides congruent, it is called equilateral 3
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Triangle notes
October 10, 2016
The relationship between angles and sides:
­ You can use the angle measures to tell if a triangle is scalene, isosceles, or equilateral too.
If a triangle has two equal angles, it must have two equal sides. Therefore, it is isosceles
If a triangle has no equal angles, it must have no equal sides. Therefore, it is scalene.
If a triangle has three equal angles, it must have three equal sides. Therefore, it is scalene.
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