http://www.ck12.org Chapter 1. Basics of Geometry
We are told there are two congruent sides, so it is an isosceles triangle. By its angles, they all look acute, so it is an
acute triangle. Typically, we say this is an acute isosceles triangle.
Watch this video for help with the Examples above.
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/52603CK-12 Foundation: Chapter1TriangleClassificationB
Vocabulary
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). Aright triangleis a triangle with one right angle. Anobtuse triangleis a triangle with one obtuse angle. An
acute triangleis a triangle where all three angles are acute. Anequiangular triangleis a triangle with all congruent
angles. Ascalene triangleis a triangle where all three sides are different lengths. Anisosceles triangleis a triangle
with at least two congruent sides. Anequilateral triangleis a triangle with three congruent sides.
Guided Practice
- How many triangles are in the diagram below?
- Classify the triangle by its sides and angles.
- Classify the triangle by its sides and angles.