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This lesson focuses on complementary and supplementary angles, essential concepts in geometry. Students will learn how to define and identify these angles through examples. Complementary angles sum to 90° while supplementary angles sum to 180°. The session will include proofs to reinforce understanding and application of these concepts. Students will work collaboratively in pairs to complete proof exercises and present their findings, enhancing their problem-solving skills in geometry.
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Warm Up • Given: Angle MOR = (3x + 7)° • Angle ROP = (4x – 1)° • MO OP • Which angle is larger, angle MOR or angle ROP? M R O P
Complementary and Supplementary Angles I CAN… • Define and identify complementary and supplementary angles • Write proofs involving complementary and supplementary angles
Complementary Angles • Two angles whose sum is 90 • A is complementary to B • JOC is the complement of COB B 38 52 A J C O B
Supplementary Angles • Two angles whose sum is 180 • A is supplementary to B • HAM is the supplement of HAB B 64 116 A H M A B
Definitions: If-then Form • If two angles form a right angle, then they are complementary. • If two angles form a straight angle, then they are supplementary.
Example 1 • Given: TVK is a right • Prove: 1 is comp. to 2 1 2 Statement Reason T X V K
Example 2 • Given: Diagram as shown • Prove: 1 is supp. to 2 1 2 Statement Reason A B C
Example 3 • The measure of one of two complementary angles is three greater than twice the measure of the other. Find the measure of each.
Example 4 • The measure of the supplement of an angle is 60 less than 3 times the measure of the complement of the angle. Find the measure of the complement.
Groups of 2 • Work with your partner to complete the proof I give you. • Write a paragraph proof. • Be prepared to present your proof to the class!!
1 3 • Given: 1 is supp. to 2 3 is supp. to 2 • Prove: 1 3 Write a paragraph proof: 2
1 3 • Given: 1 is comp. to 2 3 is comp. to 2 • Prove: 1 3 Write a paragraph proof: 2
A B D C • Given: A is supp. to B C is supp. to D B D • Prove: A C Write a paragraph proof:
A B D C • Given: A is comp. to B C is comp. to D B D • Prove: A C Write a paragraph proof:
Theorem • If two angles are supplementary to the same angle, then they are congruent. • If 1 is supp. to 2 and 3 is supp. to 2, then 1 3. 1 3 2
A Theorem B D C • If two angles are supplementary to congruent angles, then they are congruent. • If A is supp. to B, C is supp. to D, and B D. then A C.
Theorem 1 3 • If two angles are complementary to the same angle, then they are congruent. • If 1 is comp. to 2 and 3 is comp. to 2, then 1 3. 2
A Theorem B D C • If two angles are complementary to congruent angles, then they are congruent. • If A is comp. to B, C is comp. to D, and B D, then A C.
Homework • p. 69 # 7 – 13, 16, 17, 21 • Read Sample Problems on pages 77 & 78 • p. 79 #1 - 9, 11, 14