3-1 DEFINITIONS

Chapter 3 Test: Tuesday Oct. 18th

Quiz: Friday Oct. 14th

PARALLEL LINES

Coplanar lines that do not intersect Symbol: ||

SKEW LINES

Non-coplanar lines

Can they be parallel? NO! Definition of parallel is “coplanar”

Can they intersect NO!

TOO

What lines are parallel? What planes are parallel? What lines are skew?

A B

D C

E

H

F

G

and AB CD

ADHE and BCGF and AB FG

THEOREM

If two parallel planes are cut by a third plane, then the lines of intersection are parallel.

X

Y

Z

A

B

C

D

If X||Y

then AB||CD

TRANSVERSAL A line that intersects two or more coplanar

lines in different points

p is the transversal of m and n Exterior angles: 1,2,8,7 Interior angles: 4,3,5,6 Alternate Interior angles (AI): 4&6,3&5 Same-Side Interior angles (SSI): 4&5, 3&6 Corresponding angles (Corr): 1&5, 4&8, 2&6,

3&7

m

n

p

1 24 3

5 678

Ways To remember:

Alt. Int. Angles make a big Z when you trace them.

SSI angles make a “bracket” or “sandwich”. Corresponding angles must be in the same

exact spot but on another pair of lines.

TOO Page 75 #2-9

Answers:2) SSI3) Corr.4) None5) Alt. Int.6) None7) Corr.8) SSI9) Alt. Int.

HOMEWORK

3.1 Definitions Worksheet Only do the problems that are numbered, some

of the worksheet is notes