Geometric Shapes

Lesson 1

angles angles angles

Let’s Discover:Triangle Cut-Apart

What do you know about triangles?

Characteristics of triangle “angles”:

The sum of the angles in any size triangle is equal

to 1800.

90

55

35

90 + 35 + 55 = 180

Example 1:

80

45

x

Example 2:

Now try these:

In triangle ABC, m ∠ CAB = 57

and m ∠ ABC = 104. Find m ∠ ACB.

EXIT CARD:If you have angles 30 and 80 degrees, what is the

measure of the third angle?

Lesson 2

triangles triangles triangles

Brainpop Video

“Types of Triangles”

Characteristics of triangle “sides”:

The sum of the two smaller sides must be

greater than the length of the third side.

Example 1:

Can the following lengths make a triangle?

4 cm, 8 cm, 14 cm

4 + 8 = 12 12 ‹ 14 so no these sides cannot make a triangle.

Can the following lengths make a triangle?

5 in, 10 in, 13 in

Example 2:

5 + 10 = 15 15 › 13 so these sides do make a triangle.

Does the following lengths form a triangle?

a. 7 ft, 19 ft, 15 ft

b. 24 mm, 20 mm, 30 mm

c. 15 in, 25 in, 45 in

d. 4 cm, 12 cm, 18 cm

e. 1 yd, 10 yd, 20 yd

Exit Card:

3-2-1

Lesson 3http://www.youtube.com/watch?v=GO20ZgUzlc0

Let’s have some fun!!

IXL - Identify complementary, supplementary, vertical, adjacent, and congruent angles (8th grade math practice)

Exit Card:

One minute talk about differences in angle relationships with a

partner.

Lesson 4

Supplementary And

Complementary

How do you use supplementary angles to find unknown angle measures?

For Example

What is the measure angle x in the figure below?

110o xo

Let’s ReviewCore Lesson

A set of stairs inclines at a 110o angle. A support beam is going to be constructed under the stairs. What angle

measure does the support need to have?

110o

xo

Any interior ray from a point on a straight angle

creates two supplementary angles.

Let’s ReviewCore Lesson

110o

xo

110o + x = 180o

x = 70o

Supplementary angles add to 180o.

-110o -110o

Let’s ReviewCore Lesson

Two angles are supplementary. If one angle measure is 82o, what is the

measure of the second angle?

x + 82o = 180o

- 82o -82o

x = 98o

Let’s ReviewGuided Practice

Find the measure of angle x below.

158o xo

Let’s ReviewExtension Activities

Andy measured two angles. One angle was 153o and one angle was 47o. Andy said that the two angles were supplemental. Is Andy correct? Explain your reasoning.

How do you use complementary angles to find unknown angle measures?

For example

What is the measure of angle x?

xo

15o

Let’s ReviewLet’s Review

A right angle measures exactly 90o.

90o

Let’s ReviewCore Lesson

Two angles are complementary. If the measure of one angle is 43o, what is the measure of the second angle?

43o + x = 90o

-43o -43o

x = 47o43o

x

Let’s ReviewGuided Practice

Two angles are complementary. If one angle measures 17o, what is the measure of the second angle?

Let’s ReviewExtension Activities

Two angles are complementary. One angle measures xo and the second angle measures (x + 16)o. Find the measures of the two angles.

Let’s ReviewQuick Quiz

Two angles are complementary. One angle measures 22o. What is the measure of the second angle?

The two angles below are complementary. What is the measure of the missing angle?

63o

xo

Exit Card:

What is the difference in supplementary and

complementary angles?