# Lesson 1.2 - PowerPoint PPT Presentation

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Lesson 1.2. Intro to Geometry. L earning T arget. I can understand basic geometric terms and postulates. 1. Points. Points do not have actual size. How to Sketch: Using dots How to label: Use capital letters. A. B. 2. Postulates. An accepted statement of fact.

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Lesson 1.2

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## Lesson 1.2

Intro to Geometry

Learning Target

I can understand basic geometric terms and postulates.

### 1. Points

• Points do not have actual size.

• How to Sketch:

Using dots

• How to label:

Use capital letters

A

B

### 2. Postulates

• An accepted statement of fact.

### 3. Line POSTULATE – Through any two points there is exactly ONE line

• Lines extend indefinitely and have no thickness or width.

• How to sketch : using arrows at both ends.

• How to name: 2 ways

(1) small script letter – line n

(2) any 2points on the line -

• Never name a line using three points -

n

A

B

C

### 4. Segment

A part of a line that consists of two endpoints and all the points in between them.

How to name: by 2 endpoints

A

B

C

### 5. Ray

• A part of a line that consists of one endpoint and all the points to one side of that endpoint.

A

B

C

How to name: 2 points with ENDPOINT FIRST

Not like this…

### 6. Collinear Points

• Collinear points are points that lie on the same line.

C

A

A

B

C

B

Non collinear

Collinear

### 7. Planes POSTULATE – Through any 3 non-collinear points there is exactly ONE plane

• A plane is a flat surface that extends indefinitely in all directions.

• How to sketch: Use a parallelogram (four sided figure)

• How to name: 2 ways

(1) Capital script letter – Plane M

(2) Any 3 non collinear points in the plane - Plane: ABCor BCA or BAC, etc.

A

M

B

C

A

B

Plane BCG

Plane ABF

Plane CDH

Etc.

D

C

E

F

H

G

### Other planes in the same figure:

Any three non collinear points determine a plane!

Plane ACG

Plane ACH

Etc.

### 8. CoplanarObjects

Coplanar objects (points, lines, etc.) are objects that lie on the same plane.

Are the following points coplanar?

A, B, C ?

Yes

A, B, C, F ?

No

H, G, F, E ?

Yes

E, H, C, B ?

Yes

A, G, F ?

Yes

C, B, F, H ?

No

### 9. Intersection of Two Lines POSTULATE

The intersection of two lines is a point.

m

Line m and line n intersect at point P.

P

n

### 10. Intersection of Two Planes POSTULATE

The intersection of two planes is exactly ONE line.

B

P

A

R

Plane P and Plane R intersect at the line