Geometric Reasoning

1. Geometric Reasoning Mahobe

2. The facts to learn

3. Angles in a triangle add up to 180o

4. Angles on a straight line add up to 180o

5. Angles around a point add up to 360o

9. base ∠’s isos ∆ =

11. ∠ sum quad Interior angles of a quadrilateral sum to 360o

12. opp∠, cyclic quad Opposite angles of a cyclic quadrilateral sum to 180o

13. Ext ∠, of cyclic quad Exterior angle of a cyclic quad equals the opposite interior angle

14. vertopp ∠s = • Vertically opposite angles are equal

15. alt ∠s // lines Alternate angles are equal if the lines are parallel

16. corr∠s // lines Corresponding angles are equal if the lines are parallel

17. Co-int∠s // lines Co-interior angles sum to 180o if the lines are parallel

18. Exterior angles of a polygon add up to 360o

19. If the polygon is regular all exterior angles are the same size Exterior angles of a polygon add up to 360o

20. ext ∠ regular pentagon Exterior angles of a regular pentagon is 72o

21. Interior angles of a polygon with n sides sum to 180(n-2)

22. Find all the other angles in this figure

30. Vertopp angles

33. A triangle formed with 2 radii is isosceles

37. The angle at the centre is twice the angle at the circumference.

38. When writing angles use 3 letters. The middle letter is where the angle is.

39. Find the angles u, v and w O Is the centre

40. O Is the centre

41. O Is the centre

42. O Is the centre

43. Find angle d

46. Calculate the size of angle ABC