Triangles

Triangles

By Kevvin Hankins

Standard

​MGSE7.G.2

Explore various geometric shapes with given conditions. Focus on creating triangles from three measures of angles and/or sides, noticing when the conditions determine a unique triangle, more than one triangle, or no triangle.​

7th Grade Mathematics| Triangles

​Learning Targets

​R. 1 I can determine what type of triangle will be constructed when given three lengths of line segments.

R. 2 I can determine if three given length measurements can be used to construct a triangle.​

7th Grade Mathematics| Triangles

Some text here about the topic of discussion

Triangle inequality theorem (video) | Khan Academy

You can open this webpage in a new tab.

Copy link

Open in new tab

Triangles

Welcome to this lesson. We will learn about triangles and their parts, and some of their properties.  

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.

Multiple Choice

Which of these triangles is equilateral?

Isosceles triangle

• An isosceles triangle has two equal sides.

• This is an example of an isosceles triangle.

Multiple Choice

Which of these triangles is isosceles?

Scalene Triangle

• A scalene triangle has no equal sides.

• This is an example of scalene triangle.

Multiple Choice

Which of these triangles is scalene?

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.

Multiple Choice

Which of these is 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

Multiple Choice

Which of these is a right triangle?

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 triangles is obtuse?

Classifying triangles two ways

• This is a right isosceles triangle.

• It has a right angle and two equal sides.

Poll

How comfortable do you feel with today's topic?

• Expert

• Competent

• Novice