LINES AND ANGLES

PARALLEL LINES

Def : line that do not intersect.

Illustration:

Notation: l || m AB || CD

lm

A

B

C

D

p. 129

Examples of Parallel Lines• Streets: Home & School

Def: Lines that intersect to form a right angle.

Illustration:

Notation: m n

Key Fact: 4 right angles are formed.

PERPENDICULAR LINES

m

n

p. 79

Transversal

Def : a line that intersects two lines at different points

Illustration:

t

Vertical Angles

Two angles that are opposite angles.

1 2

3 4

5 6

7 8

t

Ð1 4Ð2 3Ð5 8Ð6 7

SUPPLEMENTARY ANGLES/LINEAR PAIR

• Two angles that form a line (sum=180)

1 2

3 4

5 6

7 8

tÐ5+6=180Ð6+8=180Ð8+7=180Ð7+5=180

Ð1+2=180Ð2+4=180Ð4+3=180Ð3+1=180

CORRESPONDING ANGLES

Two angles that occupy corresponding positions.

Top Left

t

Top Left

Top Right

Top Right

Bottom Right

Bottom Right

Bottom Left

Bottom Left

Ð1 5Ð2 6Ð3 7Ð4 8

1 2

3 4

5 6

7 8

Alternate Interior AnglesTwo angles that lie between parallel lines on

opposite sides of the transversal

t

Ð3 6Ð4 5

1 2

3 4

5 6

7 8

Alternate Interior AnglesFind the measures of the missing angles

82

?

t

98 82

ALTERNATE EXTERIOR ANGLES Two angles that lie outside parallel lines on

opposite sides of the transversal

t

Ð2 7Ð1 8

1 2

3 4

5 6

7 8

Find the measures of the missing angles

Alternate Exterior Angles

120

?

t

60 120

Consecutive Interior Angles• Two angles that lie between parallel lines on the

same sides of the transversal

t

Ð3 +5 = 180Ð4 +6 = 180

1 2

3 4

5 6

7 8

p. 131 & 143

B Y H E M A N T H YO S H I K A