VocabularyEquilateral: All sides equal. All angles 60 degrees
Isosceles: 2 equal sides. 2 equal angles. Scalene: No equal sides. No equal angles. Acute: An angle less than 90 degrees Obtuse: An angle more than 90 degrees Right: An angle at exactly 90 degrees |
Today's Target: Understand the triangle naming method, and begin find missing angles within a triangle
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Naming of Triangles
Triangles have 2 different things affecting their names. The first is whether it is an equilateral, Isosceles, or Scalene, but also depending if the angles for those triangles are acute or obtuse.
Math Antics - Triangles
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Acute Scalene: no equal sides, only acute angles
Acute Isosceles: 2 equal sides, only acute angles. Equilateral: All equal sides, all acute angles Right Scalene: no equal sides, 1 right angle Right Isosceles: 2 equal sides, 1 right angle Obtuse Scalene: no equal sides, 1 obtuse angle Obtuse Isosceles: 2 equal sides, 1 obtuse angle |
Remembering the naming method
Trying to memorize or cram these triangle names is complicated. The easier method to learning them is to remember the rules for how they're named.
The root word in this name is "Equal." This triangle has all equal sides and angles. So, for Equilateral, think Equal. Also, there is only 1 equilateral type triangle.
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Isosceles: Think of an evergreen tree. An isosceles triangle has 2 equal sides.
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Scalene: This triangle has no equal sides or angles. Nothing matches.
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If it has an obtuse or right angle add that angle type before the triangle type.
[Angle] + [Triangle Type] = Triangle's name
Only an equilateral triangle does not need this because an equilateral will always have acute angles.
Identify and Name
As a group, lets identify the names of the following triangles.
If the amount of lines on a triangle match with any side, it means they are the same length
If the amount of lines on a triangle match with any side, it means they are the same length
The Missing Angle
Find the missing Angle
Below are some triangles with missing angles, using what you have learned, find out the missing angle.