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Lesson 1.1 (And Introduction to Measuring Angles) Objective: Recognize points, lines, line segments, rays, angles, and triangles, and measure segments,

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Presentation on theme: "Lesson 1.1 (And Introduction to Measuring Angles) Objective: Recognize points, lines, line segments, rays, angles, and triangles, and measure segments,"— Presentation transcript:

1 Lesson 1.1 (And Introduction to Measuring Angles) Objective: Recognize points, lines, line segments, rays, angles, and triangles, and measure segments, angles, and classify angles

2 Points: Represented by capital letters (Draw 3 points and label them) Lines: Lines are made up of points and are straight. Arrows are drawn on the ends to show that the lines extend infinitely far in both directions. All lines are straight and extend infinitely far in both directions. Basic Definitions

3 More on Lines: Lines can be named based on any two points. Let’s take a look at an example: Name the line in 3 different ways. Basic Definitions A B l

4 Number Line: A number line is formed when a numerical value is assigned to each point on a line. Example: Draw a number line from -2 to 3 using one tick mark per integer. Basic Definitions

5 Line Segment: Like lines, segments are made up of points and are straight, however, segments have a definite beginning and end. Line Segments are named by their endpoints. Examples: Name the following line segments Basic Definitions S R X P Q

6 Rays: Like lines and segments, rays are made up of points and are straight. A ray differs from a line or segment in that it begins at an endpoint and extends infinitely far in only one direction. Examples: Basic Definitions D C K J L M P

7 Note: It is important to keep in mind that when we name a ray, we name the endpoint first! This makes it clear as to where the ray begins. Name the following rays: D C K J L M P

8 Angles: Two rays that have the same endpoint form an angle. Def. An Angle is made up of two rays with a common endpoint. This point is called the vertex of the angle. The rays are called sides of the angle. Examples: Basic Definitions C 2 A P H 1 B 2 S T

9 Naming Angles When naming an angle with 3 letters you must name the vertex in the middle! Every time…no exceptions! Examples: Name the following angles C 2 A P H 1 B 2 S T

10 a. b. c. Example #1 C A B D m E

11 Draw a diagram in which the intersection of with is segment Example #2

12 Segments can be measured using tools such as rulers or meter sticks, and often, segments found on number lines can be measured by subtracting the ending and starting value. Example: Measuring Segments P Q

13 Angles are measured using Protractors, and in this course we will be measuring angles in degrees. The measure (or size) of an angle is the amount of turning you would do if you were at the vertex, looking along one side, and then turned to look along the other side. (A surveyor’s transit works in a similar way!) Measuring Angles

14 Angles can be classified into four groups: Classifying Angles by Size Name Acute AnglesObtuse AnglesRight AnglesStraight Angles Definition An angle whose measure is greater than 0 and less than 90° 0< x < 90° An angle whose measure is greater than 90° and less than 180° 90°

15 Lesson 1.1 Worksheet Homework

16 Lesson 1.2 Measurement of Segments and Angles Objective: Measure segments, angles, classify angles by size, name the parts of a degree, recognize congruent angles and segments

17 Yesterday we touched briefly on measuring segments and angles, and classifying angles … Today, we are going to break down measuring angles into degrees, minutes, and seconds and discuss angle congruencies. Recap…

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20 Every hour of the day is divided into 60 minutes. Each minute is divided into 60 seconds. Similarly, each degree of an angle is divided into 60 minutes. And each minute of an angle is divided into 60 seconds. 60’ = 1° 60” = 1’ Parts of a Degree

21 1. 87½° = ° = 3. 90° = ° = Practice… ½ of a degree is ½ of 60’= 30’ Answer: 87° 30’.4° = 4/10 and 4/10 of 60 = 24 Answer: 60° 24’ Answer: 89° 60’ Answer: 179° 59’60”

22 Clock Handout Time! Important Notes: A circle = 360°, and 360 ÷ 12 = 30° Every 15 minutes the hour hand moves ¼ of 30° (that’s 7.5°) One way to determine how many degrees the hour hand has moved is to calculate what fraction (out of 60 minutes) your minute hand is at. …. Let’s try this ….

23 Example #1: Find the measure of the angle formed by the hands of a clock at 11:40 Between 8 and 9 = 30° Between 9 and 10 = 30° Between 10 and 11 = 30° Total = 90 °

24 Example #1: Find the measure of the angle formed by the hands of a clock at 11:40 Now we have to consider the 40 minutes. 40/60 = 2/3 (So the hour hand has moved 2/3 of the way between 11 and 12) 2/3 of 30 ° = 20° Final Answer: 90° + 20° = 110 °

25 Example #2: Given:

26 Def. Congruent ( ) angles are angles that have the same measure Congruent Angles and Segments S R X P 3 cm Def. Congruent ( ) segments are segments that have the same measure 3 cm 42° A B

27 We use identical tick marks to indicate congruent angles and segments. Example #3: Name the 4 pairs of congruent parts Tick Marks G H K R Y Z XW S T ^ ^

28 Lesson 1.2 Worksheet Homework


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