Vocabularyperpendicular lines right angleparallel lines acute angleskew lines obtuse anglevertical angles straight

angletransversal complementary

anglessupplementary

angles

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Angles formed by two intersecting lines are equal to 90°, the lines are perpendicular lines.

Lines in the same plane that do not intersect at all are parallel lines.

Skew lines do not intersect, and yet they are also not parallel.

Vertical angles

1)are the opposite angles formed by two intersecting lines.

2)When two lines intersect, two pairs of vertical angles are formed.

3)Vertical angles have the same measure, so they are congruent.

A transversal is a line that intersects two or more lines.

1)Eight angles are formed when a transversal intersects two lines.

2)When those two lines are parallel, all of the acute angles formed are congruent, and all of the obtuse angles formed are congruent.

3)These obtuse and acute angles are supplementary.

1 2

3 45 6

7 8

An angle’s measure determines the type of angle it is.

A right angle is an angle that that measures exactly 90°. Thesymbol indicates a right angleAn acute angle is an anglethat measures less than 90°

An obtuse angle is an anglethat measures more than 90°but less than180°

A straight angle is an anglethat measures 180°

If the sum of the measures of two angles is90°, then the angles are complementary angles. If the sum of the measures of twoangles is 180°, then the angles are supplementary angles.

Line n line p. Find the measure of the angle.

2 =

3 =

130°

50°

4 = 130°

Line x line y. Find the measure of the angle.

3 =45°

2 3 135°5 64

7

x y6 =

4 =

Tell whether each angle is acute, right, obtuse or straight and the degrees of each angle.

A. B. C.

right angle 90°

obtuse angleGreater than 90 °

acute angleLess than 90 °

Use the figure to name the following. 1) one pair of complementary angles

Since 30° + 60° = 90°,

m OMP = 30° and m OMR = 60°

OMP and OMR are complementary.

60° 90°

30°60°

N Q

P

OR

M

2) one pair of supplementary angles m QMP = 90° and m PMR = 30° + 60° = 90°

Since 90° + 90° = 180°, QMP and PMR are supplementary.

Use the figure to name the following.

1) one pair of complementary angles

45° 100°

35°55°

N Q

P

OR

M

2) one pair of supplementary angles

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