How do you find angle measurements in this

triangle?

90

(4x + 7)

(8x - 1) 3x

2x -5

x + 11

In this lesson you will learn how to find the measure of an angle in a triangle by using the

other two angles.

Let’s ReviewLet’s Review

3

21

1

2

3

180

Let’s ReviewLet’s Review

x + 11 + 2x - 5 + 3x

3x + 2x + x + 11 -5

6x + 6

Let’s ReviewA Common Mistake

angle 1 + angle 2 + angle 3 90

1

23

Let’s ReviewCore Lesson

65

47

x

a

cb

47 + 65 + x = 180112 + x = 180

x = 68angle b = 680

Let’s ReviewCore Lesson

X + 11 + 2x - 5 + 3x = 1806x + 6 =180

6x = 174x = 29

(3x)

(2x -5)

(x + 11)c

b

a

Let’s ReviewCore Lesson

(3x)

(2x -5)

(x + 11)c

b

a

Angle a = x + 11

Angle a = 29 + 11

Angle a = 400

In this lesson you have learned how to find the measure of an angle in a triangle by using the

other two angles.

Let’s ReviewGuided Practice

Find the measurement of angle m.

(8x + 2)

(4x) (2x + 10)

m

o

n

Let’s ReviewExtension Activities

Find the measure of angle b by solving for x

65

80

x

a

cb

Let’s ReviewExtension ActivitiesFind the measure of angle c

(3x)

(2x – 11)

(2x + 27)

c

b

a

Let’s ReviewExtension Activities

Angle b is three times the measure of angle a. Angle c is two times the measure of angle a. What are the measures of all the angles in triangle abc?

ac

b

Let’s ReviewQuick Quiz

Triangle ABC has angle that measure 78⁰ and 270

. What is the measure of the third angle?

Determine all three angle measurements in Triangle XYZ that has angles that measure (2x – 15)0, (x – 5)0 and 420.