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LINES AND ANGLES

Lines and Line Segments Angles Types of Angles

Line: A B A Acute angle Right angle
Line segment: A B Arm A
Ray: A B Angle A
O B 60° 90°
Vertex Arm O B O
B
Pair of Lines Obtuse angle Straight angle

Intersecting Lines Parallel Lines Transversal Line A 130° 180°
l A m A O B
l 1 O B
m
O B n Reflex angle Complete angle
l 2
Lines l and l Lines l and m are Line AB is transversal A O B
1
2
intersect each other. parallel to each other. to the lines m and n. B 360° A
230° O
Corresponding Angles Pair of Interior Angles on the
10 Same Side of Transversal
12 Complementary Angles
9 The sum of pair
11 of angles ∠1 and 1 p R
Pair of angles ∠9 and ∠10, ∠2, which are on 2 70° Q
∠11 and ∠12 which are on the the same side of a m l 20°
same side of a transversal are transversal is 180°. O P
corresponding angles. That is ∠1 + ∠2 = 180°. ∠POQ and ∠ROQ are
complementry.
Alternate Angles

Alternate Interior Angles Alternate Exterior Angles Supplementary Angles
6 8
1 3 2 4 C
5 7 100°
Pair of interior angles ∠1 and Pair of exterior angles ∠5 and 80°
∠3, ∠2 and ∠4 which are on the ∠6, ∠7 and ∠8 which are on the A B D
opposite sides of a transversal opposite sides of a transversal are ∠ABC and ∠DBC are
are alternate interior angles. alternate exterior angles. supplementry angles.

Adjacent Angles Linear Pair of Angles Vertically Opposite Angles
Common
A arm A P
B Q 2
Common 1 3
Vertex Q 4
O C P O R B
∠1 = ∠3 and ∠2 = ∠4 are two pairs of
∠AOC = ∠AOB + ∠BOC ∠POQ and ∠ROQ are a linear pair. vertically opposite angles.

163 Lines and Angles