3.1 Classifying Triangles

3.1 Classifying Triangles

*note that an equiangular triangle can only have three 60 - degree angles!

Multiple Choice

Classify this triangle.

• obtuse

• right

• acute

Multiple Choice

Classify this triangle.

• acute

• right

• obtuse

Multiple Choice

Classify this triangle.

• obtuse

• right

• acute

*Not that this is intentionally worded to reflect that equilateral triangles are special forms of isosceles triangles.

Multiple Choice

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What is the name of this kind of triangle?

• Equilateral

• Scalene

• Isosceles

Multiple Choice

Name this triangle by the side length

• scalene

• isosceles

• equilateral

• right

Multiple Choice

Which type of triangle is pictured?

• Equilateral

• Isosceles

• Scalene

Multiple Choice

What type of triangle is this?

• Scalene

• Isosceles

• Equilateral

Multiple Choice

What type of triangle is this?

• Equilateral

• Isosceles

• Scalene

Classifying Triangles

When we talk about types of triangles, we usually refer to 7 different types of Triangles. To name each type, we use the triangle's angle classification and then its side classification to come up with a single name:

Acute scalene

Acute isosceles

right scalene

right isosceles

obtuse scalene

obtuse isosceles

and the single named equilateral.

Special note about Equilateral Triangles

For reasons that we will get into in the next couple of lessons, the only way a triangle can be equilateral is for it to also be equiangular. Because we know that all equilateral triangles are made up of three 60 degree angles, we do not bother to reference their angle measures when referring to them.

Multiple Choice

• A
• B
• C
• D

Multiple Choice

• Equilateral Triangle
• Scalene Triangle
• Isosceles Triangle
• Right Triangle

Multiple Choice

Which type of triangle is pictured?

• Equilateral Triangle
• Right Isosceles Triangle
• Obtuse Scalene Triangle
• Obtuse Equilateral Triangle

Multiple Choice

• A
• B
• C
• D

Multiple Choice

• A
• B
• C
• D

Multiple Choice

• A
• B
• C
• D

Multiple Choice

• A
• B
• C
• D

Open Ended

Open Ended

Explain why all equiangular triangles are know to be acute.

Multiple Choice

Which of the truth statements applies to the following statement?

equiangular triangles are also right triangles.

• Always true

• Sometimes true

• never true

Multiple Choice

Which of the truth statements applies to the following statement?

equilateral triangles are isosceles triangles

• Always true

• Sometimes true

• never true

Multiple Choice

Which of the truth statements applies to the following statement?

Right triangles are scalene triangles

• Always true

• Sometimes true

• never true