7-2 Measuring and Classifying Angles What You’ll Learn To measure and describe angles To measure and describe angles To work with pairs of angles To work with pairs of angles

Measuring and Describing Angles An angle (<) is formed by two rays with a common endpoint. An angle (<) is formed by two rays with a common endpoint. The angle below can be named <ECD or <C The angle below can be named <ECD or <C A vertex is the point of intersection of two sides of an angle or figure. A vertex is the point of intersection of two sides of an angle or figure. The vertex of this angle is C The vertex of this angle is C E C D

Measuring Angles Step 1: place your protractor on the vertex of the angle Step 1: place your protractor on the vertex of the angle Step 2: make sure that one side of the angle passes through zero on one of the protractor’s scale Step 2: make sure that one side of the angle passes through zero on one of the protractor’s scale Step 3: read the same scale where it intersects the second side of the angle Step 3: read the same scale where it intersects the second side of the angle

Measure the following Angles

Classifying Angle by their Measures Obtuse Angle - an angle with a measure greater than 90 degrees and less than 180 degrees Obtuse Angle - an angle with a measure greater than 90 degrees and less than 180 degrees Right Angle - an angle with a measure equal to 90 degrees Right Angle - an angle with a measure equal to 90 degrees Acute Angle - an angle with a measure greater than 0 degrees and less than 90 degrees Acute Angle - an angle with a measure greater than 0 degrees and less than 90 degrees

Working with Pairs of Angles Complementary angles - two angles whose measures have a sum of 90 degrees Complementary angles - two angles whose measures have a sum of 90 degrees

Working with Pairs of Angles Supplementary angles - two angles whose measures have a sum of 180 degrees Supplementary angles - two angles whose measures have a sum of 180 degrees

If mQSN is equal to 90º, then QSP and PSN are _________________. A. complementary angles B.supplementary angles

If AEC is a straight angle, then BEC and AEB are ________________. If AEC is a straight angle, then BEC and AEB are ________________. A.complementary angles B. supplementary angles B. supplementary angles

Finding Complements/Supplements The measure of <A is 37. Find the measure of the supplement The measure of <A is 37. Find the measure of the supplement X + 37 = 180 X + 37 = 180 X = 180 – 37 X = 180 – 37 X = 143 X = 143 Find the complement of < A Find the complement of < A X + 37 = 90 X + 37 – 37 = 90 – 37 X = 53

AEC and CED are supplementary. CED is equal to 62º

Working with Pairs of Angles Adjacent angles share a vertex and a side but have no interior points in common Adjacent angles share a vertex and a side but have no interior points in common Angles AEB and CEB are adjacent Angles AEB and CEB are adjacent Adjacent angles are supplementary Adjacent angles are supplementary

Working with Pairs of Angles Vertical angles are formed by two intersecting lines and are opposite of each other Vertical angles are formed by two intersecting lines and are opposite of each other Vertical angles have equal measures Vertical angles have equal measures Angles AEB and DEC are vertical angles Angles AEB and DEC are vertical angles Congruent angles are angles that have the same measure Congruent angles are angles that have the same measure Angles AEB and DEC are congruent Angles AEB and DEC are congruent

Find the Angle Measures <AED = 128 find the following angles: <AED = 128 find the following angles: AEB AEB BEC BEC CED CED