Classifying Triangles and the Triangle Sum Theorem

Mrs. Angel's lesson covers classifying triangles by their sides and angles, including equilateral, isosceles, scalene, acute, right, obtuse, and equiangular triangles. The lesson also explains the triangle sum theorem, which states that the interior angles of a triangle add up to 180 degrees. Students are guided through exercises to classify triangles and solve for unknown angles using equations.

What do you call a triangle where all three sides are of equal length?

• Isosceles

• Scalene

• Equilateral

• Right

Tags

CCSS.4.G.A.2

If a triangle has two sides of equal length, what is it called?

• Acute

• Scalene

• Isosceles

• Equilateral

Tags

CCSS.4.G.A.2

Which type of triangle has no sides of equal length?

• Scalene

• Isosceles

• Equilateral

• Right

Tags

CCSS.4.G.A.2

What is the name of a triangle where all angles are less than 90 degrees?

• Right

• Obtuse

• Acute

• Equiangular

Tags

CCSS.4.G.A.2

A triangle with one angle measuring exactly 90 degrees is called a?

• Obtuse triangle

• Acute triangle

• Right triangle

• Scalene triangle

Tags

CCSS.4.G.A.2

What do you call a triangle with one angle greater than 90 degrees?

• Equilateral triangle

• Obtuse triangle

• Acute triangle

• Right triangle

Tags

CCSS.4.G.A.2

If a triangle has all angles equal, what is it called?

• Equiangular

• Isosceles

• Scalene

• Equilateral

Tags

CCSS.8.G.A.5

What is the sum of the interior angles of any triangle?

• 270 degrees

• 180 degrees

• 90 degrees

• 360 degrees

Tags

CCSS.8.G.A.5

If two angles of a triangle are 30 degrees and 84 degrees, what is the measure of the third angle?

• 66 degrees

• 76 degrees

• 96 degrees

• 86 degrees

Tags

CCSS.8.G.A.5

Given a triangle with angles (x + 48), (x + 78), and 60 degrees, what is the value of x?

• -3

• 3

• 5

• 7

Tags

CCSS.8.G.A.5