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Triangles Reference Chart – Types and Angles

Six triangle types — acute, right, obtuse, equilateral, isosceles, and scalene — are each defined by angle or side properties on a reference chart.
Year groups
Lower Secondary, Primary, Years 4–7
Pages
2
File type
PDF
Preparation
Print ready

Updated Oct 23, 2025

Subject
Geometry, Maths
Topic
Triangles, Geometry
Resource types
Diagrams, Charts, Graphic Organizers, Anchor Charts, Posters, Classroom Decor, Teacher Tools
Preparation
Print ready

From the author

About this resource

2D Geometry Shapes Triangles Reference Chart

Learning about triangles doesn’t have to be tricky. This reference chart makes it easy for students to understand the different types of triangles, including acute, right, and obtuse angles, as well as equilateral, isosceles, and scalene sides. The chart comes in a full-colour version that works beautifully as a classroom wall display, on a whiteboard, or even projected digitally. There is also a black-and-white version that fits perfectly in student binders or interactive notebooks, providing a handy reference sheet that students can keep at their desks.

This resource is ideal for lessons on 2D shapes and triangle classification. It’s especially helpful for visual learners who benefit from seeing concepts clearly illustrated, and it makes a useful addition to maths centres, classroom displays, or study materials. Using the chart regularly can help students build confidence in recognizing and naming different triangle types while reinforcing key geometry vocabulary and concepts. Teachers will also appreciate the time saved, since the chart is ready to print and use immediately. It works best for students in grades 3 through 6, but it can also serve as a helpful review tool for older students. Whether you display the colour chart on your maths wall or provide the black-and-white version for individual students, this reference chart is a flexible and practical resource for any geometry unit.

In the classroom

Teaching tips & learning objectives

Learning objectives

  • Classify a triangle as acute, right, or obtuse based on its largest angle.

  • Classify a triangle as equilateral, isosceles, or scalene based on its side lengths and angle equality.

  • Use the chart's definitions to identify and name a given triangle correctly.

Teaching tips

  • Display the colour version on a maths wall as an ongoing visual reference during a geometry unit.

  • Give students the black-and-white version to keep in a maths notebook or interactive notebook for quick reference during independent work.

  • Have students sort a set of triangle cutouts into acute/right/obtuse and equilateral/isosceles/scalene groups using the chart's definitions as a check.

Skills covered

  • Angle-based triangle classification — students use the chart's angle-measure definitions to sort triangles into acute, right, and obtuse.

  • Side-based triangle classification — students use the chart's side-and-angle-equality definitions to sort triangles into equilateral, isosceles, and scalene.

  • Geometry vocabulary — the chart reinforces precise terms for each triangle type and its defining property.

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