A triangle is a two-dimensional, closed shape with exactly three straight sides, three vertices, and three angles. The defining attributes remain unchanged when a triangle is rotated, reflected, resized, or drawn with unequal sides, so appearance and orientation do not determine whether a shape is a triangle; formal angle measurement and more advanced classification are not included here.
On this page:
- Learn “Identify triangles” with a detailed explanation of the concept
- Master “Identify triangles” with unlimited, free practice problems
- Download (or modify) a free worksheet on Identify triangles you can use at home or in class with practice problems that scaffold and explore “Identify triangles” from different perspectives.
- Start working on adaptive units like “Geometry Basics - Intro” that introduce, teach, or practice “Identify triangles” to maximize your learning.
Detailed Explanation: Identify triangles
A triangle is a closed, flat shape with:
- exactly 3 straight sides
- exactly 3 vertices (corners)
- exactly 3 angles
The shape can be turned, flipped, made bigger or smaller, or have sides of different lengths. It is still a triangle if it has these three features.
Example:
Look at a shape that is tilted to one side. It has three straight sides, three corners, and three angles. Its sides are not all the same length.
Check it step by step:
- Is the shape closed? Yes.
- Does it have exactly 3 straight sides? Yes.
- Does it have exactly 3 vertices? Yes.
- Does it have exactly 3 angles? Yes.
Because all the checks are true, the shape is a triangle.
Learn by doing: Identify triangles
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Your results
Practice with unlimited practice problems
Practice:
Identify Shapes 2D - Count Triangles
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Download/Modify Free Grade 2 'Identify triangles' Worksheet
Print this free 'Identify triangles' worksheet to practice this skill away from the computer. Click 'Modify' to easily customize this worksheet to your exact needs.
This Worksheet Includes:
- Identify Shapes 2D - Count Triangles
- Identify Shapes 2D - Count Triangles (Real World)
- Polygons - Number of Sides to Name
- Shapes - 2D Simple (Real World)
Units Teaching This Skill
These adaptive units introduce, teach, or reinforce this skill (Identify triangles) through scaffolded problems that grow in difficulty as concepts are understood.