8.G.5
Use informal arguments to establish facts about the angle sum and exterior angle of triangles, about the angles created when parallel lines are cut by a transversal, and the angle-angle criterion for similarity of triangles. For example, arrange three copies of the same triangle so that the sum of the three angles appears to form a line, and give an argument in terms of transversals why this is so.
| 1. | By degrees: Calculate triangle angles from a given ratio | |
| 2. | Line Dancing - equal corresponding angles, true/false | |
| 3. | Line Dancing - perpendicular and parallel lines, true/false | |
| 4. | Line Dancing - right angles, parallel lines, true/false | |
| 5. | Top Of The Tower Triangle - calculate size of angles in isosceles triangle, angle sum of a triangle | |
| 6. | Ancient Angles - calculate size of base angles in isosceles triangle, angle sum of a triangle | |
| 7. | Tricky Triangles 4 - calculate reflex angle of equilateral triangle | |
| 8. | Tricky Triangles 3 - calculate size of angles in isosceles triangle, angle sum of a triangle, reflex angles | |
| 9. | Tricky Triangles 2 - calculate size of angles in isosceles triangle, angle sum of a triangle | |
| 10. | Tricky Triangles 1 - calculate size of angles in isosceles triangle, angle sum of a triangle | |
| 11. | Phoebe's Triangle Theorems 4 - sides and angles of equilateral triangles | |
| 12. | Phoebe's Triangle Theorems 3 - equal angles opposite equal sides | |
| 13. | Phoebe's Triangle Theorems 2 - exterior angle of triangle | |
| 14. | Shape Up! 7 - equilateral triangle, angle sum of triangle | |
| 15. | Phoebe's Triangle Theorems 1 - angle sum of a triangle |