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This lesson teaches how to calculate angle measures of vertical angles formed by intersecting lines. It also covers the concept of linear pairs and provides examples and practice problems.
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ESSENTIAL OBJECTIVE Calculate Angle Measures of Angles formed by Intersecting Lines
Vertical Angles: two angles that are formed by intersecting lines and are not adjacent to each other. VOCABULARY
Vertical Angles: two angles that are formed by intersecting lines and are not adjacent to each other.
Vertical Angles: two angles that are formed by intersecting lines and are not adjacent to each other.
Linear Pair: Two adjacent angles whose opposite rays form a straight line.
Linear Pair: Two adjacent angles whose opposite rays form a straight line.
Example 1 Determine whether the labeled angles are vertical angles, a linear pair,or neither. SOLUTION Identify Vertical Angles and Linear Pairs b. c. a. a. 1 and2 are a linear pair. b. 3 and4 are neither. 5 and6are vertical angles c.
Linear Pair Postulate: If two angles form a linear pair, then they are supplementary
Example 2 Find the measure of RSU. SOLUTION RSU andUST are supplementary. To findmRSU,subtract mUST from180°. mRSU =180°– mUST = 180°–62° = 118° Use the Linear Pair Postulate
Vertical Angles Theorem Vertical Angles are Congruent ( )
Vertical Angles Theorem Vertical Angles are Congruent ( )
Example 3 Find the measure of CED. SOLUTION AEBandCED are vertical angles. CED AEB, somCED = mAEB = 50°. Use the Vertical Angles Theorem
Example 4 Findm1, m2,andm3. SOLUTION Find Angle Measures m2 = 35° m1 = 180° – 35° = 145° m3 = m1= 145°
Checkpoint Findm1, m2,andm3. Find Angle Measures 1. m1 = 152°; m2 = 28°;m3 = 152° ANSWER 2. m1 = 56°; m2 = 124°;m3 = 56° ANSWER 3. m1 = 113°; m2 = 67°;m3 = 113° ANSWER
Checkpoint Use Algebra with Angle Measures Find the value of the variable. 4. ANSWER 43 5. ANSWER 16 6. ANSWER 5
Example 5 SOLUTION Algebraic expressions are measures of vertical angles, you can write the following equation. –2y = –2 Use Algebra with Vertical Angles Find the value of y. (4y– 42)° = 2y° 4y– 42 – 4y= 2y – 4y –42 = –2y –42 21 = y –2 .
Determine whether the angles are complementary, supplementary, or neither. Also tell whether the angles are adjacent or nonadjacent. 1. 2.
Determine whether the angles are complementary, supplementary, or neither. Also tell whether the angles are adjacent or nonadjacent. 1. ANSWER complementary; adjacent 2. ANSWER neither; nonadjacent
3. mR = 27° 4. mT = 11° 5. In the figure at the right, ABDand DBC are complementary angles. Find the value of x. Find the measures of a complement and a supplement of the angle.
3. mR = 27° 63°; 153° ANSWER 4. mT = 11° 79°; 169° ANSWER 5. In the figure at the right, ABDand DBC are complementary angles. Find the value of x. ANSWER x = 7 Find the measures of a complement and a supplement of the angle.