5.1 Angles of Triangles

5.1 Angles of Triangles

by Mary Lett

​Objective and Standards

• ​Students will be able to classify triangles by their angles and sides and use angle sum theorems to find interior or exterior angle values.

• ​HSG-CO.C.10 Prove theorems about triangles

• ​HSG-MG.A.1 Use geometric shapes, their measures, and their properties to describe objects.

Multiple Choice

An acute triangle has __________ angles that each measure less than 90°.

• one

• two

• three

• four

Multiple Choice

An isosceles triangle has _________ equal sides.

• one

• two

• three

• four

Multiple Choice

A right triangle has one angle that measures _______ and two acute angles.

• 90°

• less than 90°

• more than 90°

• 180°

Multiple Choice

An ____________ triangle has three equal sides.

• isosceles

• equilateral

• scalene

Multiple Choice

An obtuse triangle has one angle that measures _____________ 90°.

• less than

• exactly

• more than

Multiple Choice

A _________ triangle has no equal sides.

• scalene

• isosceles

• equilateral

Multiple Choice

Which type of triangle is pictured?

• A

• B

• C

• D

Multiple Choice

Which type of triangle is pictured?

• A

• B

• C

• D

Multiple Choice

Which type of triangle is pictured?

• A

• B

• C

• D

Multiple Choice

Which type of triangle is pictured?

• A

• B

• C

• D

​Corollary

• ​A corollary to a theorem is a statement that can be easily proved from the theorem.

Multiple Choice

Find the measure of each angle indicated.

• 139°

• 66°

• 138°

• 116°

Multiple Choice

• 47

• 57

• 53

• 133

Multiple Choice

The Triangle Sum Theorem states that the sum of all angles in a triangle is ______. 

• 45°
• 90°
• 180°
• 360°

Multiple Choice

Which of the following terms best describes Angle d?

• Remote interior angle
• Corresponding angle
• Exterior angle
• Interior angle

Multiple Choice

Find the indicated angle. (What is ?)

• 91°

• 81°

• 89°

• 109°

Multiple Choice

Solve for x

• 60

• 120

• 40

• 65