1. Lines, Angles, and Triangles
Geometry
Topic 2
Lines, Angles, and Triangles

2. Table of Contents
Recommended Instructional Design and Planning Continuum Slide 3
Vocabulary …………………………………………………………………….……………..Slides 4 – 22
Reporting Category Practice Items ………………….…………………………….Slides

4. Vocabulary

5. Mathematically Speaking!
Choose 3-4 vocabulary words for the day. Throughout the lesson, as students respond to your questions or are presenting a problem on the board, mark a tally when a vocabulary word is used accurately. This can be turned into a competition among groups or between periods.
Examples of accuracy
vertical angles vs opposite angles
hypotenuse vs the long side
congruent vs same

6. Vertical angles – the non adjacent angles formed by two intersecting lines.
∠1 and ∠3 are vertical angles. ∠2 and ∠4 are vertical angles.

7. Transversal – a line that intersects at least two other lines.
Line 𝑡 is a transversal.

8. Parallel Lines

9. Indirect proof – a proof in which the statement to be proved is assumed to be false and a contradiction is shown.

10. Hypotenuse – the side opposite the right angle in a right triangle.

11. Interior angle – an angle formed by two sides of a polygon with a common vertex.

12. Auxiliary line – a line drawn in a figure to aid in a proof.

13. Exterior angle – an angle formed by one side of a polygon and the extension of an adjacent side.

14. Isosceles triangle – a triangle with at least two congruent sides.

15. Equilateral triangle – a triangle with three congruent sides.
Equiangular triangle – a triangle with three congruent angles.

16. Triangle Inequality Theorem - The sum of the lengths of any two sides of a triangle is greater than the length of the third side.
Example:
AB + BC > AC AC + BC > AB
AB + AC > BC

17. Congruent Triangles Two possible congruence statements: ∠ABC ≅ ∠FED
∠BCA ≅ ∠EDF

18. SSS Triangle Congruence Postulate

19. SAS Triangle Congruence Postulate

20. ASA Triangle Congruence Postulate

21. AAS Triangle Congruence Theorem

22. HL Right Triangle Congruence