Bell WOrk

1. Bell WOrk • PROJECT 1 FINAL DRAFT IS DUE TOMORROW! • Any questions on review packet?? Solve for x Which lines are parallel?

2. Parallel & Perpendicular lines October17, 2011

3. Theorem 3-7 a If 2 lines are || to the same line, then they are parallel b c If a||b and b||c, then a||c

4. Theorem 3-8 c In a plane, If 2 lines are | to the same line, then they are || a b

5. | transversal theorem(Theorem 3-9) In a plane, if a line is | to 1 of 2 parallel lines, then it is also | to the other If n | l and l||m , then n | m

6. Why theorem 3-9 must be in a plane The perpendicular transversal theorem states that the lines must be in plane. The diagram at the right shows why. In a rectangular solid line AC and line BD are parallel. Line EC is perpendicular to line AC, but it is not perpendicular to line BD. In fact, line EC and line BD are skew because they are not in the same plane

7. GIVEN: In a plane c | b, b | d, d | a PROVE: c | a • Lines c and d are perpendicular to line b, So c || d. Because two lines perpendicular to the same line are || (Theorem 3-8) • It is given that d | a. Therefore, c | a because a line that is perpendicular to one of two parallel lines is also perpendicular ( | Transversal Theorem)

8. Main Street intersects Avenue A and Avenue B. Avenue A || Avenue B. Avenue A is also | to Main Street. How are Avenue B and Main Street related? Explain. Main Street | Avenue B because Of theorem 3-9

9. a||b by theorem 3-8 a||b

10. Suppose you are laying tiles. You place several different rectangles together to form a larger rectangle. a. BCis parallel to DF, DF is parallel to GH . What is the relationship between BC and GH? Explain. b. BKis parallel to EL. GH is perpendicular to BK . What is the relationship between GH and EL?

11. Try This: • A student says that according to Theorem 3-8, LINE AB and LINE BC must be parallel because they are both perpendicular to LINE BF . Explain the student’s error.

12. Homework • PROJECT 1 DUE TOMORROW!!!! • REVIEW PACKET DUE TOMORROW!!! • WB pg. 71