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Practice congruence statements, theorems, and constructions related to triangles in geometry. Learn to identify isosceles and equilateral triangles, and solve for missing measures.
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Refer to the figure. Complete the congruence statement.ΔWXY Δ_____ by ASA. ? A.ΔVXY B.ΔVZY C.ΔWYX D.ΔZYW 5-Minute Check 1
Refer to the figure. Complete the congruence statement. ΔWYZ Δ_____ by AAS. ? A.ΔVYX B.ΔZYW C.ΔZYV D.ΔWYZ 5-Minute Check 2
Refer to the figure. Complete the congruence statement. ΔVWZ Δ_____ by SSS. ? A.ΔWXZ B.ΔVWX C.ΔWVX D.ΔYVX 5-Minute Check 3
What congruence statement is needed to use AAS to prove ΔCAT ΔDOG? A. C D B. A O C. A G D. T G 5-Minute Check 4
Content Standards G.CO.10 Prove theorems about triangles. G.CO.12 Make formal geometric constructions with a variety of tools and methods (compass and straightedge, string, reflective devices, paper folding, dynamic geometric software, etc.). Mathematical Practices 2 Reason abstractly and quantitatively. 3 Construct viable arguments and critique the reasoning of others. CCSS
You identified isosceles and equilateral triangles. • Use properties of isosceles triangles. • Use properties of equilateral triangles. Then/Now
legs of an isosceles triangle • vertex angle • base angles Vocabulary
___ BCA is opposite BA and A is opposite BC, so BCA A. ___ Congruent Segments and Angles A. Name two unmarked congruent angles. Example 1
___ BC is opposite D and BD is opposite BCD, so BC BD. ___ ___ ___ ___ Congruent Segments and Angles B. Name two unmarked congruent segments. Example 1
A. Which statement correctly names two congruent angles? A.PJM PMJ B.JMK JKM C.KJP JKP D.PML PLK Example 1a
A.JP PL B.PM PJ C.JK MK D.PM PK B. Which statement correctly names two congruent segments? Example 1b
Since QP = QR, QP QR. By the Isosceles Triangle Theorem, base angles P and R are congruent, so mP = mR . Use the Triangle Sum Theorem to write and solve an equation to find mR. Find Missing Measures A. Find mR. Example 2
Find Missing Measures B. Find PR. Since all three angles measure 60, the triangle is equiangular. Because an equiangular triangle is also equilateral, QP = QR = PR. Since QP = 5, PR = 5 by substitution. Example 2
A. Find mT. A. 30° B. 45° C. 60° D. 65° Example 2a
B. Find TS. A. 1.5 B. 3.5 C. 4 D. 7 Example 2b
Find Missing Values ALGEBRA Find the value of each variable. Example 3
Find the value of each variable. A.x = 20, y = 8 B.x = 20, y = 7 C.x = 30, y = 8 D.x = 30, y = 7 Example 3
Given:HEXAGO is a regular polygon. ΔONG is equilateral, N is the midpoint of GE, and EX || OG. Prove:ΔENX is equilateral. ___ Apply Triangle Congruence Example 4
Given: HEXAGO is a regular hexagon.NHE HEN NAG AGN Prove: HN EN AN GN ___ ___ ___ ___ Proof: Statements Reasons 3. HE EX XA AG GO OH 1. HEXAGO is a regular hexagon. 1. Given 2. NHEHENNAGAGN 2. Given 3. Definition of regular hexagon 4. ΔHNE ΔANG 4. ASA Example 4
Proof: Statements Reasons 5. HN AN, EN NG 5. ___________ ? 6. HN EN, AN GN 6. Converse of Isosceles Triangle Theorem 7. HN EN AN GN 7. Substitution A. Definition of isosceles triangle B. Midpoint Theorem C. CPCTC D. Transitive Property Example 4