Triangles are a type of 2D, or flat, shape.
All triangles have three sides and three angles.
An angle is the measure in degrees where two sides meet.
Triangles with different angles have different names.
The 3 angles in a triangle always add up to 180°.
But depending on how big and small each of these angles are, triangles can be named either acute, obtuse, or right triangles.
Let's learn each of these names:
In an acute triangle, all three angles are less than 90°.
Tip: Acute angles are angles less than 90°.
So it's easy to remember that acute triangles have only acute angles.😺
Obtuse triangles have one angle that's greater than 90°.
Tip: Obtuse angles are angles that are greater than 90°. So it makes sense that obtuse triangles have an obtuse angle!
Right triangles have one angle that's exactly 90°.
Tip: A right angle, or 90° angle, is marked with a small square where the lines meet.
Great job! 😀
Do you think you can tell the different types of triangles apart? 😺
What kind of triangle is this? 👇
That’s right! 💪 This is an obtuse triangle! ✅
We know this is an obtuse triangle because one angle is greater than 90°.
Let’s try another one!
Is this an acute, obtuse, or right triangle?
Great! 🎉 This is a right triangle!
A right triangle has one angle that measures 90°.
Let’s try one more!
Identify this triangle as acute, obtuse, or a right triangle.
Perfect! This is an acute triangle because all of its angles measure less than 90°.
Great job! 😀 Now, you know how to identify acute, right and obtuse triangles!
Now, complete the practice. 💪 You'll learn more and remember for longer.