1.11. Triangle Classification http://www.ck12.org
1.11 Triangle Classification
Here you’ll learn how to classify a triangle based on its angles and sides.
What if you were given the angle measures or side lengths of several triangles and were asked to group them based
on their properties? After completing this Concept, you’ll be able to classify a triangle as right, obtuse, acute,
equiangular, scalene, isosceles, and/or equilateral.
Watch This
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/52602CK-12 Foundation: Chapter1TriangleClassificationA
Watch this video starting at around 2:30.
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/1276James Sousa: Types of Triangles
Guidance
Atriangleis any closed figure made by three line segments intersecting at their endpoints. Every triangle has three
vertices(the points where the segments meet), threesides(the segments), and threeinterior angles(formed at each
vertex). All of the following shapes are triangles.
You might have also learned that the sum of the interior angles in a triangle is 180◦. Later we will prove this, but for
now you can use this fact to find missing angles. Angles can be classified by their size: acute, obtuse or right. In
any triangle, two of the angles will always be acute. The third angle can be acute, obtuse, or right. We classify each
triangle by this angle.
Right Triangle:When a triangle has one right angle.