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Triangle

DEFINITION: A triangle  is ANY 2D shape with THREE (3) SIDES and THREE (3) ANGLES and can be classified into the following three regular shapes:

Right Triangle Acute Triangle Obtuse Triangle

OPTIONAL: INTERESTING FACTS

INTERESTING FACTS:

There are three types of "SPECIAL" triangles based on their SIDES and ANGLES:

  • An EQUILATERAL triangle is a triangle with THREE equal sides and THREE equal angles that are always 60 degrees. NOTE: An equilateral triangle is a special kind of isosceles triangle.
  • An ISOSCELES triangle is a triangle with at least TWO equal sides and TWO equal angles. NOTE: Isosceles is derived from the Greek iso (same) and skelos (leg). An isosceles right triangle is a special kind of isosceles triangle.
  • A SCALENE (ACUTE) triangle is a triangle with NO equal sides and NO equal angles.


    MEMORIZATION TIP: Notice the pattern for each special TRIANGLE:
    • 3 x 3 - EQUILATERAL - has 3 sides and 3 angles
    • 2 x 2 - ISOSCELES - has 2 sides and 2 angles
    • 0 x 0 - SCALENCE - has 0 side and 0 angle

      NOT to be confused with the patterns for regular 2D SHAPES:
    • 4 x 4 - QUADRILATERAL - has 4 sides and 4 angles
    • 3 x 3 - TRIANGLE - has 3 sides and 3 angles
    • 0 x 0 - CIRCLE - has 0 side and 0 angle