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Triangle Classification

In this topic, we cover the classification of triangles based on their angles and the lengths of their sides.

Topic: Classification by Angles

  • A triangle is a closed figure with three line segments and three angles.
    Triangles can be classified as acute, right, or obtuse using the measures of their angles

  • An acute triangle has only acute angles (less than 90°).
    An obtuse triangle has exactly one obtuse angle (more than 90°).
    A right triangle has one right angle (equal to 90°)

  • The sum of the measures of the angles in any triangle is 180°
    We can use this to find the unknown angle measures

Topic: Classification by Lengths of Sides

  • Triangles can be classified by the lengths of their sides

  • A scalene triangle has no congruent sides. An isosceles triangle has at least two congruent sides. An equilateral triangle has three congruent sides

  • The perimeter of a triangle is the sum of its three sides
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