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What are Equilateral, Isosceles, and Scalene Triangles?
What are equilateral, isosceles, and scalene triangles?
Summary
- In an equilateral triangle, all sides are congruent and all angles are congruent
- In an isosceles triangle, two sides are congruent and the two angles opposite of those sides are congruent
- In a scalene triangle, no sides and no angles are congruent
- Sides that are congruent are the same length
- Angles that are congruent have the same measure

Notes
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- All sides are the same length in an equilateral triangle
- 'Congruent' simply means 'the same'
- The equals sign with a squiggly line over it is the symbol for 'congruent'
- The bars over JK, KL, and JL means they are line segments, or sides
- All angles are equal in an equilateral triangle
- The slanted-looking 'L' is the symbol for 'angle'
- The Triangle Sum Theorem says the sum of all angles in a triangle must be 180 degrees
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- Only two sides are the same length in an isosceles triangle
- 'Congruent' simply means 'the same'
- The equals sign with a squiggly line over it is the symbol for 'congruent'
- The bars over MO and MN means they are line segments
- The two equal angles in an isosceles triangle sit opposite of the two congruent sides
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- Only two sides need to be congruent in an isosceles triangle
- All three sides are congruent in an equilateral triangle!
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- No sides or angles are the same length in a scalene triangle
- 'Congruent' simply means 'the same'