1. Building Blocks of Geometry
8-1
Building Blocks of Geometry
Course 1
Warm Up
Problem of the Day
Lesson Presentation

2. Warm Up Solve 1. x + 1 = 5 2. 2 = 2x 3 3. x – 7 = 6 4. = 1 14 2 1 3
4. =
1 3 3
2 3
1 2 1
1 4
2 3
1 3 14
x 3
4 5 2
2 5

3. Problem of the Day
Draw a clock face that includes the numerals 1–12. Draw two lines that do not intersect and that separate the clock face into three parts so that the sums of the numbers on each part are the same.

4. Learn to describe figures by using the terms of geometry.

5. Vocabulary
point
line
plane
line segment
ray

6. The building blocks of geometry are points, lines, and planes.
A point is an exact location. P point P, P
A point is named by a capital letter.
A line is a straight path that line AB, AB, extends without end in A B line BA, BA opposite directions.
A line is named by two points on the line.
A plane is a flat surface that plane LMN, extends without end in all plane MLN, directions plane NLM
A plane is named by three points on the plane that are not on the same line. M N L

7. Additional Example 1: Identifying Points, Lines, and Planes
Use the diagram to name the geometric figure.
A. three points
M, N, and P Q N P R M
Five points are labeled: points M, N, P, Q, and R.
B. two lines
PR and NR
You can also write RP and RN.

8. Additional Example 1: Identifying Points, Lines, and Planes
Use the diagram to name the geometric figure.
C. a point shared by two lines
point R
Point R is a point on PR and NR. Q N P R M
D. a plane
plane QRM
Use any three points in the plane that are not on the same line Write the three points in any order.

9. Use the diagram to name the geometric figure.
Check It Out: Example 1
Use the diagram to name the geometric figure.
A. three points
S, T, and U
Five points are labeled: points S, T, U, V, and W. V S U W T
B. two lines
UW and SW
You can also write WU and WS.

10. Use the diagram to name the geometric figure.
Check It Out: Example 1
Use the diagram to name the geometric figure.
C. a point shared by two lines
point W
Point W is a point on WS and WU. V S U W T
D. a plane
plane VUT
Use any three points in the plane that are not on the same line Write the three points in any order.

11. A line segment is. line segment XY, XY, made of two endpoints
A line segment is line segment XY, XY, made of two endpoints Y line segment YX, YX and all the points between X the endpoints.
A line segment is named by its endpoints.
A ray has one endpoint ray JK, JK From the endpoint, the ray J K extends without end in one direction only.
A ray is named by its endpoint first followed by another point on the ray.

12. Additional Example 2: Identifying Line Segments and Rays
Use the diagram to give a possible name to the figure.
A. three different line segments C A B
AB, BC, and AC
You can also write BA, CB, and CA.
B. three ways to name the line
AB, BC, and AC
You can also write BA, CB, and CA.

13. Additional Example 2: Identifying Line Segments and Rays
Use the diagram to give a possible name to the figure.
C. six rays C A B
AB, AC, BC, CB,
CA, and BA
D. another name for ray AB AC
A is still the endpoint C is another point on the ray.

14. A. three different line segments
Check It Out: Example 2
Use the diagram to give a possible name to the figure.
A. three different line segments F D E
DE, EF, and DF
You can also write ED, FE, and FD.
B. three ways to name the line
DE, EF, and DF
You can also write ED, FE, and FD.

15. D. another name for ray DE
Check It Out: Example 2
Use the diagram to give a possible name to the figure.
C. six rays F D E
DE, EF, DF, FE,
FD, and ED
D. another name for ray DE DF
D is still the endpoint F is another point on the ray.

16. Lesson Quiz
Use the diagram to name each geometric figure.
1. three points
2. two lines
3. a point shared by a line and a ray
4. a plane
Possible answer: A, B, C
Possible answer: AD, CE
Possible answer: F
Possible answer: plane AEC