Triangle Sum Theorem

Do Now

What is the value of x in this equation?

3 x + 4 = − 62

Record your answer and fill in the bubbles on your answer document.
Be sure to use the correct place value.

Lesson Objective

Demonstration of

Learning

(7.11 C) I will be able to write and solve
equations using geometry concepts,
including the sum of the angles in a
triangle, and angle relationships

Date

Given 4 problems, I will be able to write and
solve equations using geometry concepts,
including the sum of the angles in a
triangle, and angle relationships 4/4 times
or with 100% accuracy.

How can you use angle relationships to solve problems?

Essential Question

Academic Vocabulary

❖ Vertical Angles
❖ Adjacent Angles
❖ Complementary Angle
❖ Supplementary Angles

Let's review from our past lessons!

​Remember the following for each problem:

Review!!!

​The front of the top story of a house is shaped like an isosceles triangle. The measure of the angle at the top of the triangle is 70°. Find the measure of each of the base angles.

​

Use the diagram and find the value of x. 

    Also, find the measures of ∠ A and ∠ B

​

Multiple Choice

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

• 45°

• 90°

• 180°

• 360°

Multiple Choice

Find the measure of the missing angle.

• 47

• 57

• 53

• 133

Multiple Choice

The measures of two angles in a triangle are shown in the diagram.

  

Which equation can be used to find the value of x?

• A  64° + 2 x = 180°

• B  2(64°) + x = 180°

• C  64° + 2x = 360°

• D  2(64°) + x = 360°

Multiple Choice

Find the measure of the indicated angle.

• $$135\degree$$  

• $$55\degree$$  

• $$45\degree$$  

• $$60\degree$$  

Multiple Choice

An isosceles triangle has base angles that each measure 52°. Which equation can be used to find b, the measure of the third angle of this isosceles triangle in degrees?

• A 104° + 2b = 180°

• B 104° + b = 180°

• C  52° + 2b = 180°

• D  52° + b = 180°