8th grade -- 9/12 & 9/19

Classifying Angles

Multiple Choice

Classify the angle.

• acute

• obtuse

• right

• straight

Multiple Choice

What kind of angle is this?

• Acute

• Obtuse

• Right

Multiple Choice

Classify the angle

• acute

• obtuse

• right

• straight

Multiple Choice

Which type of angle is this?

• Acute

• Obtuse

• Right

• Straight

Multiple Choice

I can classify angles as acute, obtuse, straight, or right.​

The angle shown is

• acute

• obtuse

• straight

• right

Multiple Choice

This angle is an example of what type of angle?

• right

• acute

• obtuse

• straight

Classifying triangles by angle measure

• When you classify triangles by their angle measures, you use the words acute, right, and obtuse.

  
  

• Let's find out what those words mean!

Acute Triangle

• An acute triangle has 

  three acute angles.

• Acute angles measure less than 90°

• This is an example of an acute triangle.

Right Triangle

• A right triangle has one right angle.

• Right angles measure exactly 90°.

• This is an example of a right triangle.

• Notice that all of the angles add up to 180 degrees.

• The angles in a triangle always add up to 180 degrees

Obtuse triangle

• An obtuse triangle has one obtuse angle.

• Obtuse angles measure more than 90°.

• This is an example of an obtuse triangle.

Multiple Choice

Which of these is an acute triangle?

Multiple Choice

Which of these is a right triangle?

Multiple Choice

Which of these triangles is obtuse?

Classifying triangles by their sides and lengths

• Triangles have special names based on their side lengths and angle measures.

  
  

  
  

• When you classify triangles by their side lengths, you use the words equilateral, isosceles, and scalene.

Equilateral Triangle

• An equilateral triangle has three equal sides.

• This is an example of a equilateral triangle.

Isosceles triangle

• An isosceles triangle has two equal sides.

• This is an example of an isosceles triangle.

Scalene Triangle

• A scalene triangle has no equal sides.

• This is an example of scalene triangle.

Multiple Choice

Which of these triangles is equilateral?

Multiple Choice

Which of these triangles is isosceles?

Multiple Choice

Which of these triangles is scalene?

Classifying triangles two ways

• This is a right isosceles triangle.

• It has a right angle and two equal sides.

Multiple Choice

Classify the triangle by angles and sides.

• Obtuse Scalene

• Obtuse Isosceles

• Acute Isosceles

• Equiangular Scalene

Multiple Choice

Classify the triangle by angles and sides.

• Equiangular Equilateral

• Right Isosceles

• Right Scalene

• Acute Isosceles

Multiple Choice

Identify the triangle by its sides and angles

• Acute Scalene

• Obtuse Equilateral

• Acute Equilateral

• Acute Isosceles

Poll

How comfortable do you feel with today's topic?

• Expert

• Competent

• Novice