Slide1: The A,B,C’s of Geometry – PART 1 4 th grade
Slide2: The Basics
Slide3: Ray
Slide4: This is Ray AB . You can also call him Ray A . Write his name as Ray AB or just AB for short . endpoint Ray There is only ONE endpoint on a RAY , and the endpoint is ALWAYS named or written first .
Slide5: Line Segment
Slide6: C D Line Segment
Slide7: C D NAMES : Line Segment CD or Line Segment DC WRITTEN : CD or DC endpoint endpoint Line Segment There are two endpoints on a LINE SEGMENT . It doesn’t matter which endpoint is named or written first.
Slide8: C D NAMES : Line CD or Line DC WRITTEN : CD or DC No endpoint! No endpoint! There are no endpoints on a LINE . It doesn’t matter which point is named or written first. Line
Slide9: Lines,Line Segments, Rays t hey cross t hey never cross t hey cross a t 90°
Slide10: s pelled ang le ….not ang el ! The sides of angles are made of rays or line segments Angle 2 rays with a common endpoint. 2 line segments with a common endpoint.
Slide11: Name an angle by 3 points. The middle point is called the vertex . Or, name it by the vertex on its own. So, the name of this angle is: Angle XYZ , Angle ZYX, or just Angle Y Angle X Y Z
Slide12: Written as: Angle XYZ, Angle ZYX Angle Y or or Angle X Y Z
Slide13: small 3 Kinds of Angles medium large a cute angle obtuse angle > 90° < 90° = 90° 0° 90° 180° Angles are measured in degrees . The symbol for degrees is ° right angle Angles “open up” from 0°
Slide14: Right Angles 0° 180° m easure exactly 90° 90°
Slide15: Acute Angles 0° 90° 180° m easure between 0° and 90° 45° is halfway b etween 0° and 90°
Slide16: Obtuse Angles 0° 90° 180° m easure between 90° and 180° 135° is halfway b etween 90° and 180°
Slide17: 0° 90° 180° 270° 360 ° “full circle” = All Angles Halfway around = 180° All the way around = 360°
Slide18: 4 Kinds ° Triangles Every triangle has 3 angles. All 3 angles add up to 180° 60° 60° 60° 9 0° different° same°
Slide19: One Picture that Puts it All Together Triangles >90° 2 sides equal all sides equal < 90° n o sides equal >90° 2 sides equal < 90° n o sides equal < 90° =90° 2 sides equal n o sides equal =90° √ √
Slide20: Quadrilaterals 4-sided shapes Trapezoid Rectangle Rhombus Parallelogram Square
Slide21: = 3 =4 =4 = 5 4 Equal Sides Opposite Sides are Parallel Opposite Sides are Equal Opposite Angles are Equal 4 right Angles This chart shows why a SQUARE is also a parallelogram, a rectangle, and a rhombus, and why they are NOT a square! Compare t hese 4
Slide22: A Rhombus looks like a Square that got pushed. A Parallelogram looks like a Rectangle that got pushed. EASY to Remember:
Slide23: Trapezoids What’s different a bout them? Trapezoids have only ONE pair of parallel sides, instead of two. These other Quadrilaterals have TWO pairs of parallel sides: This pair of sides isn’t p arallel.
Slide24: Symmetry A shape has symmetry if it can be folded in half along a straight line AND the two halves completely overlap, or cover, each other. Some shapes have no have symmetry: Scalene triangle – 0 lines of symmetry Rectangle, star, equilateral triangle – many lines of symmetry Isosceles triangle, arrow, butterfly – = 1 line of symmetry Some shapes have more than 1 line of symmetry: ❶ ❷ ❸
Slide25: End of Part 1