3. Obtuse Angles The Basics of Angles Reflex Angles Acute Angles Right Angles 2. 1. 5. 4. 3. 6. Move through the topics at your own pace The numbers are just suggestions. The Project

4. Right Angles A right angle is a “square corner”. A right angle is 90°. A right angle looks like this:

5. More About Right Angles! Only right angles have a square at the vertex. Right angles can be rotated many ways. But as long as there is a square corner, the angle is a right angle.

6. Let’s Take a Quiz! Is this a right angle? Yes No

7. Awesome!!! Let’s see how you do on the next question.

8. Sorry… Remember that right angles often have a square at the vertex. Let’s try again.

9. How about this angle? Is it a right angle? YesNo

10. Great!!! You really know your right angles!

11. Sorry… Remember: If an angle is not a “square corner”, it is not a right angle. Let’s try again.

12. Let’s try one more question… Fill in the blank: A right angle is _____ degrees. A. 90° B. 30° C. 120° B. 30° C. 120° B. 30° C. 120°

13. Fantastic!!! A right angle is always 90°. Click here and choose a new area of angles to explore.

14. That’s too bad  A right angle is always 90°. Let’s try again.

15. The Basics of Angles An angle is formed when two lines or two line segments meet at a point. Here’s an angle formed by 2 rays: Here’s an angle formed by 2 line segments:

16. More Basics of Angles… This is the symbol for an angle: Angles are measured in degrees. For example, if an angle is 35 degrees, we write it like this: 35° Notice the symbol for degrees.

17. And More Basics of Angles All angles have a vertex. The vertex is like the “elbow” of the angle. I’m a vertex.

18. How We Mark an Angle… Sometimes we make a curve at the vertex to show measurement. When the angle is a right angle, we often draw a square at the vertex. 45° 90°

19. Very Important Info!!! Even though we share the same vertex, I measure a different angle than that arc over there. Even though we share the same vertex, I measure a different angle than that green arc over there. I measure a different angle than that red arc over there.

20. Angles Are All Around Us Click here to learn about the types of angles.

21. Acute Angles An acute angle is greater than 0° and less than 90°. An acute angle is “more closed” than a right angle. Right Angle “Square Corner” Acute Angle

22. PacMan and the Acute Angle This is Pac-Man. Pac-Man’s mouth is an acute angle. Acute angle Isn’t Pac-Man cute? Acute

23. Let’s Take a Quiz! Can you pick the acute angle? A. B. C. D.

24. Great! You really know your acute angles!

25. Sorry… An acute angle is between 0° and 90°. An acute angle is “more closed” than a right angle.

26. Let’s Try Another Question True or False: An acute angle is less than 90°. True False

27. Sorry, Let’s Review Acute Angles An acute angle is greater than 0° and less than 90°. An acute angle is “more closed” than a right angle. Right Angle “Square Corner” Acute Angle

28. Excellent! You’re getting good at this!

29. One More Question… Which one of these is an acute angle? 1. 2. 3. 4.

30. Great! You really know your acute angles! Click here to check out other types of angles.

31. Sorry… An acute angle is between 0° and 90°. An acute angle is “more closed” than a right angle.

32. Reflex Angles Reflex angles are between 180° and 360°. A 180° angle is a straight line. A 360° angle is a completely closed angle. Reflex angles are in between. 180° 360°

33. Examples of Reflex Angles 270° 260° 240° 210° 335°

34. Let’s Check Your Reflexes! Which one of these is an reflex angle? 1. 2. 3. 4. 45° 340° 90° 30°

35. Wow!!! Great job! Now try one more.

36. Sorry, Let’s Review Reflex Angles Reflex angles are between 180° and 360°. A 180° angle is a straight line. A 360° angle is a completely closed angle. Reflex angles are in between. 180° 360°

37. Examples of Reflex Angles 270° 260° 240° 210° 335°

38. Let’s See If You Know This One A reflex angle is… A. Between 0° and 90°. D. Between 90° and 180°. B. Between 180° and 360°. C. Between 90° and 360°.

39. Sorry, Let’s Review Reflex angles are between 180° and 360°. A 180° angle is a straight line. A 360° angle is a completely closed angle. Reflex angles are in between. 180° 360°

40. Examples of Reflex Angles 270° 260° 240° 210° 335°

41. Great Job! One More Question The two lines below form two angles. Which angle is the reflex angle? The Green One! The Green One! The Orange One! The Orange One!

42. Sorry, Let’s Review Reflex angles are between 180° and 360°. A 180° angle is a straight line. A 360° angle is a completely closed angle. Reflex angles are in between. 180° 360°

43. Examples of Reflex Angles 270° 260° 240° 210° 335°

44. Stupendous!!! You really know about reflex angles. Click below to return to the main menu.

45. Obtuse Angles An obtuse angle is open more than a right angle. But an obtuse angle is more closed than a straight line. An obtuse angle is between 90° and 180°.

46. Angle Diagram This diagram shows the different types of angles from the starting point.This diagram shows the different types of angles from the starting point. Red shows acute angles.Red shows acute angles. Green shows obtuse angles.Green shows obtuse angles. Purple shows reflex angles.Purple shows reflex angles. Yellow shows a right angle.Yellow shows a right angle. AcuteObtuse Reflex I’m a right angle. Starting Line Note: An angle’s starting line is different every time. We judge the angle on how many degrees it opens up.

47. More About Obtuse Angles Remember this diagram? The green area shows obtuse angles.The green area shows obtuse angles. AcuteObtuse Reflex I’m still a right angle Starting Line Note: An angle’s starting line is different every time. We judge the angle on how many degrees it opens up.

48. Let’s Take a Quiz! Can you pick the obtuse angle? A. B. C. D.

49. Sorry, Let’s Review Obtuse Angles An obtuse angle is open more than a right angle. But an obtuse angle is more closed than a straight line. An obtuse angle is between 90° and 180°.

50. Sorry  This one was tricky. We know the angle is not obtuse for 2 reasons. –The angle has a square at the vertex. –The angle is a “square corner”. Both of these facts make it a right angle. Let’s try again.

51. Great! Let’s try another.

52. An Obtuse Question How many degrees are in a obtuse angle? A. An obtuse angle is between 90 and 180 degrees. B. An obtuse angle is between 0 and 90 degrees. C. An obtuse angle is 90 degrees. D. An obtuse angle is between 180 and 360 degrees.

53. Sorry, Let’s Review Obtuse Angles An obtuse angle is open more than a right angle. But an obtuse angle is more closed than a straight line. An obtuse angle is between 90° and 180°.

54. Way to Go! Knowing how many degrees are in an obtuse angle is as important as knowing what it looks like.

55. A Truly Obtuse Question True or False: This angle is obtuse. True False

56.  I have some good news and some bad news. The Bad News: If you thought this was a reflex angle, you were wrong. Pay attention to the measurement arc. The Good News: If the measurement arc was on the other part of the angle, it would be a reflex angle.

57. YES! You still knew it was an obtuse angle even though it was rotated. You are a clever kid!

58. The Project Your mission is to create a collage. You will use a large piece of paper. Divide the paper into 4 sections like this: Right ObtuseReflex Acute Label the four sections like this…

59. Making the Angles Collage Cut out pictures of the 4 types of angles. Draw in the vertex, measurement arc, and lines with a magic marker, crayon or paintbrush. Make it beautiful. We will post these in the classroom for the world to see! Click here for a small example.

60. Right Reflex Obtuse Acute

61. Angle Collage Checkbric 1. Did I write my name on the paper? 2. Did I divide the paper into 4 sections? 3. Did I label the sections: Right, Acute, Obtuse, and Reflex? 4. Did I include at least 5 examples of each type of angle? 5. Did I mark all lines or line segments? 6. Did I draw a dot for all the vertexes? 7. Did I draw measurement arcs for each angle? 8. Did I put my own personal flavor into the project? 9. Is my project neat? 10. Is my project beautiful?