Types of Triangle
Triangles are classified by their sides as equilateral, isosceles or scalene, and by their angles as acute, right or obtuse.
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Triangles are classified by their sides as equilateral, isosceles or scalene, and by their angles as acute, right or obtuse.
- Isosceles has two equal sides and angles
- Scalene has no equal sides
- A right triangle has one 90 degree angle
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Types of Triangle?
Within Mathematics, which covers numbers, algebra, geometry, trigonometry and statistics from first principles to exam level, this topic explains Types of Triangle. Maths builds step by step, so each topic here gives you a rule, a picture and a quick check you can use on homework and in exams.
Check that you can explain Types of Triangle in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Types of Triangle gives you a reliable method you will reuse in later maths units, in science lessons and in data work.
Types of Triangle in detail
Triangles are classified by their sides and angles. An equilateral triangle has three equal sides and three 60° angles, an isosceles triangle has two equal sides and two equal base angles, and a scalene triangle has no equal sides or angles.
By angle, a right-angled triangle has one 90° angle, an acute triangle has all angles less than 90° and an obtuse triangle has one angle greater than 90°. Recognising the type tells you which facts you can use, such as Pythagoras' theorem in right-angled triangles or equal angles in isosceles ones.
How the interactive helps you understand Types of Triangle
Watch the triangle in the interactive. Use any sliders or buttons it offers to change the values and see how the triangle responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Types of Triangle.
Real-life uses and examples
- Explain Types of Triangle to a friend with a simple picture, such as a row of tiles or a bag of sweets.
- Spot Types of Triangle in exam questions, where it often sits inside a short word problem.
- Check a homework answer about Types of Triangle by estimating first, then working it out step by step.
Common mistakes to avoid
- Memorising the steps for Types of Triangle without checking why they work.
- Forgetting units, signs or brackets when you apply Types of Triangle.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Types of Triangle
What is Types of Triangle?
Triangles are classified by their sides as equilateral, isosceles or scalene, and by their angles as acute, right or obtuse.
What are the most important points about Types of Triangle?
The main points are: Isosceles has two equal sides and angles; Scalene has no equal sides; A right triangle has one 90 degree angle.
Why is Types of Triangle useful?
Understanding Types of Triangle gives you a reliable method you will reuse in later maths units, in science lessons and in data work.
How can I practise Types of Triangle?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Types of Triangle?
Related topics in Mathematics include Congruence, Perimeter and Area, Area of a Circle.