Classify Triangles by Angles and Sides

Classify Triangles by Angles and Sides

Classify by Sides

• All three sides alike = equilateral

• Two sides alike = isosceles

• No sides alike = scalene

Classify by Angles

• Two angles in a triangle are always acute so it's the third angle that helps us classify the triangle

• Acute - all 3 angles are less than 90 degrees

• Obtuse - one angle is greater than 90 degrees (and the other two are acute)

• Right - one angle is 90 degrees (and the other two are acute)

​Obtuse Isosceles Triangle

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​Isosceles Right Triangle

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​Scalene Right Triangle

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​Acute Isosceles Triangle

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Multiple Choice

Which of the following is NOT a way to classify a triangle by its angles

• Right

• Scalene

• Acute

• Obtuse

Multiple Select

Please select ALL the ways a triangle can be classified by its sides.

• Equilateral

• Scalene

• Isosceles

• Right

Multiple Choice

Please classify the triangle by its angles

• acute

• obtuse

• right

Multiple Choice

Please classify the triangle by its sides

• equilateral

• isosceles

• scalene

Open Ended

Find the missing angle

Open Ended

Classify the triangle by its sides

Multiple Choice

Classify the triangle by its sides and angles

• isosceles, right

• scalene, obtuse

• isosceles, acute

• scalene, right

• equilateral, obtuse

Multiple Choice

Classify the triangle by its sides and angles

• isosceles, acute

• scalene, obtuse

• scalene, right

• equilateral, obtuse

Poll

A triangle can be both equilateral and obtuse

• True

• False

Poll

A triangle can be both scalene and right

• True

• False

Poll

A triangle can be both acute and obtuse

• True

• False

Poll

All triangles have at least two acute angles

• True

• False

Multiple Select

Which of these classifications can NEVER happen?

• Isosceles Right

• Obtuse Scalene

• Obtuse Equilateral

• Right Equilateral

• Acute Isosceles