Basic Mathematics for College Students

9.2 Parallel and Perpendicular Lines 731

b.To find the measures of the angles in the figure, we evaluate the expressions
and for.

The measures of the angles labeled in the figure are 140° and 40°.

140° 40°

120°20° 120°80°

3 x20°3( 40 °)20° 3 x80°3( 40 °)80°

3 x20° 3 x80° x40°

1. a. and , and , and , and b. , , , and c. and
   , and 2. ,,,,
   , , and 3. , 4.8°


2. a.30° b.110°, 70°

m(4)50°m(1)50° m(2)130°  1  Y 3  Z

 6  7  3 m(5)50°m(7)130°m(6)130°m(3)130°

 1  3  2  4  8  6  7  5  2  7  3  6  2

ANSWERS TO SELF CHECKS

SECTION 9.2 STUDY SET

VOCABULARY

Fill in the blanks.

1. Two lines that lie in the same plane are called
   . Two lines that lie in different planes are
   called.


2. Two coplanar lines that do not intersect are called
   lines. Two noncoplanar lines that do not
   intersect are called lines.


3. lines are lines that intersect and form
   right angles.


4. A line that intersects two coplanar lines in two
   distinct (different) points is called a.


5. In the figure below, and are interior
   angles.


6. In the figure above, and are
   angles.

CONCEPTS

7. a.Draw two parallel lines.
   Label them and.

b. Draw two lines that are not parallel.

Label them and .l 1 l 2

l 1 l 2

 2  6

14

23

58

67

 4  6

8. a.Draw two perpendicular lines.
   Label them and.

b. Draw two lines that are not

perpendicular. Label them and.

9. a.Draw two parallel lines cut by a
   transversal. Label the lines and
   and label the transversal.

b. Draw two lines that are not parallel and cut

by a transversal. Label the lines and

and label the transversal.

10. Draw three parallel lines.
    Label them , , and.
    In Problems 11–14, two parallel lines are cut by a transversal. Fill
    in the blanks.


11. In the figure below, on the left,.
    When two parallel lines are cut by a transversal,
    angles are congruent.


12. In the figure below, on the right,. When two
    parallel lines are cut by a transversal,
    angles are congruent.

2 1

A

B

E

F

C

 1   2

ABC  BEF

l 1 l 2 l 3

l 3

l 1 l 2

l 3

l 1 l 2

l 1 l 2

l 1 l 2