Pre-AP Geometry

1. Pre-AP Geometry Unit 1 Points, Lines, Planes, and Angles

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7. Introduction to Geometry Geometry (Greek γεωμετρία; geo = earth, metria = measure) is a part of mathematics concerned with questions of size, shape, and relative position of figures and with properties of space. Geometry is one of the oldest sciences.

8. Introduction to Geometry Geometry is a type of math used to measure things that are impossible to measure with devices. For example, no one has been able take a tape measure around the earth, yet we are pretty confident that the circumference of the planet at the equator is 24,901.473 miles. The first known case of calculating the distance around the earth was done by Eratosthenes around 240 BC.

9. Introduction to Geometry The study of Geometry includes proofs. Proofs are not unique to Geometry. They could have been done in Algebra or delayed until Calculus. The reason that high school geometry almost always spends a lot of time with proofs is that the first great Geometry textbook, "The Elements," was written by Euclid, exclusively with proofs.

10. Introduction to Geometry This course, for the most part, is based on Euclidean geometry. "Euclidean" (or "elementary") refers to the book "The Elements" written over 2,000 years ago by a man named Euclid.

11. Introduction to Geometry Euclid started with some basic concepts. He built upon those concepts to create more and more concepts. His structure and method influence the way that geometry is taught today.

12. Introduction to Geometry This course will include more than just facts about geometric objects; the ability to "prove" that a particular answer is correct using logic and reason is the most important part of this course.

13. Basic Figures Point • A point is a geometric element that has position but no dimensions and is used to define an exact location in space. • A point has no volume, area, or length, making it a zero dimensional object. • A point is defined by its coordinates.

14. Basic Figures Line • A line can be described as an ideal zero-width, infinitely long, perfectly straight curve (the term curve in mathematics includes "straight curves") containing an infinite number of points. • In Euclidean geometry, exactly one line can be found that passes through any two points.

15. Basic Figures Equidistant - equally distant from any two or more points.

16. Suppose that you and a friend are partners in a game in which you must locate various clues to win. You are told to pick up your next clue at a point that: • Is as far from the fountain as from the oak tree • and • 2. Is 10 m from the telephone pole. • You locate X, which satisfies both requirements, but grumble because there simply isn’t any clue to • be found at X. • Is there another location that satisfies both requirements? Basic Figures 10m X Equal distances Discussion in GSP

17. Review Quiz • Which language does the word “geometry” come from and what does it mean? • What is the circumference of the Earth at the equator? (exact value is preferred, but the nearest 1000 is acceptable) • Who wrote the book “The Elements”? • Which geometric element has dimensions of zero? • How many points does it take to define a line?

18. Written Exercises 1.1, p. 3: # 1 - 5

19. Points, Lines and Planes Lesson 1.2 Pre-AP Geometry

20. Points, Lines, and Planes The three most basic figures in geometry are points, lines, and planes. This lesson illustrates how these three basic figures relate to one another.

21. Objectives Use the undefined terms point, line, and plane. Draw representations of points, lines, and planes. Use the terms collinear, coplanar, and intersection.

22. Vocabulary Point A geometric element that has position but no dimension. A point is defined by its coordinates. Symbol: · A Line A line can be described as an ideal zero-width, infinitely long, perfectly straight curve containing an infinite number of points. Symbol: (The term curve in mathematics includes "straight curves")

23. Vocabulary Plane A plane is a two-dimensional surface that is perfectly flat, is infinitely vast, and infinitesimally thin. Undefined term A term, such as point, line, plane, and space, that is accepted without definition.

24. Vocabulary Space Theset of all points. The unlimited area which extends in all directions and within which all things exist. Intersect To meet or cross at a point.

25. Vocabulary Collinear Lying on the same straight line. Collinear points lie along a straight line. Any two points are always collinear. Coplanar Lying in the same plane. A set of points in space is coplanar if the points all lie in the same plane. Note: Collinear points are automatically coplanar, but coplanar points are not necessarily collinear.

26. Points Things that we can use to represent a point: a marble

27. Lines Things that we can use to represent a line: a taut piece of string

28. Plane Things that we can use to represent a plane: a sheet of paper a poster board

29. Intersecting Planes Things that we can use to represent intersecting planes: the sides of a cardboard box

30. Practice Quiz - True or False ends at P. Point S is on an infinite number of lines. A plane has no thickness. Collinear points are coplanar. Planes have edges. Two planes intersect in a line segment. Two intersecting lines meet in exactly one point. Points have no size.

31. Problem Set 1.2Written Exercisesp.7: # 2 – 26 even, 27 - 36

32. Lesson 1.3: Segments, Rays, and Distance Pre-AP Geometry

33. Points, Lines, and Planes Line Segment Two points (called the endpoints) and all the points between them that are collinear with those two points Named line segment AB, AB, or BA line AB segment AB  A B A B

34. Length of a segment Length of BC is stated as BC. It is the distance between points B and C. On a number line, length of a segment is found by subtracting the coordinates of the endpoints. On a coordinate plane, length of a segment is found using the distance formula D =

35. Examples Find the length between 5 and -3 on the number line Find the distance of segment AB if A(-3, 5) and B(2, -7)

36. Postulates • Postulate: statement that is accepted without proof • Segment Addition Postulate • If B is between A and C, then AB + BC = AC • Ruler Postulate • The points on a line can be paired with the real numbers in such a way that any two points can have the coordinates 0 and 1 • Once a coordinate system has been chosen in this way, the distance between any two points equals the absolute value of the difference of their coordinates.

37. Examples E F G EG = 7x + 3 EF = 3x + 8 FG = 2x + 1 Find x: Find EG: Find EF: Find FG:

38. Segment Length terms Congruent- two objects that have the same size and shape. We use the symbol ≅ to show that two objects are congruent. Congruent segments- two segments with equal lengths. Example: DE ≅ FG Midpoint of a segment: a point that divides a segment into two congruent segments. Midpoint formula: M = ( ) Segment bisector: A line, segment, ray, or plane which intersects a segment at its midpoint.

39. Points, Lines, and Planes Ray Part of a line that starts at a point and extends infinitely in one direction. Initial Point Starting point for a ray. Ray CD, or CD, is part of CD that contains point C and all points on line CD that are on the same side as of C as D “It begins at C and goes through D and on forever”

40. Points, Lines, and Planes Opposite Rays If C is between A and B, then CA and CB are opposite rays. Together they make a line. A C B

41. Lesson 1.3 homework • P. 15 # 2-40 evens

42. Lesson 1.4: Angles

43. Parts of an angle Sides of an angle are made up of rays The rays meet at a point called the vertex vertex sides

44. Naming an angle An angle can be named by the vertex, by the 3 points on the angle: the side, the vertex and the other side, or a number inside the angle. The angle can be named ∠GHI, ∠IHG, ∠H, or ∠1 G I 1 H

45. Classifying angles Acute angle: Angle measuring greater than 0° and less than 90°. Obtuse angle: Angle measuring greater than 90° and less than 180° Right angle: An angle measuring exactly 90° Straight angle: An angle measuring exactly 180°

46. Angle Postulates • Protractor Postulate: On AB in a given plane, choose any point O between A and B. Consider OA and OB and all the rays that can be drawn from O on one side of AB. These rays can be paired with real numbers from 0 to 180 in a way such that: a. OA is paired with 0, and OB with 180 b. If OP is paired with x, and OQ with y, the m∠POQ = │x - y │ • Angle addition postulate: -If B lies on the interior of ∠AOC, then m ∠AOB + m∠BOC = m∠AOC -If ∠AOC is a straight angle, then m∠AOB+m ∠BOC = 180.

47. Angle Vocabulary • Congruent Angles • Two angles with equal measures • Adjacent angles • Angles which share a vertex and a common side, but no common interior points • Angle bisector • A ray which divides an angle into two congruent, adjacent angles

48. Congruence symbols and drawing conclusions Do not assume anything in geometry. Just because two segments look equal does not mean that they are.

49. Postulates and Theorems Relating Points, Lines, and Planes Lesson 1.5 Pre-AP Geometry

50. Postulates A point is defined by its location. A line contains at least two points. A plane contains at least three points not all in one line. Space contains at least four points not all in one plane.