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2. Lesson Menu Five-Minute Check (over Lesson 9–4) Main Idea and Vocabulary Key Concept: Angles of a Quadrilateral Example 1:Find a Missing Angle Measure Key Concept: Classifying Quadrilaterals Example 2:Classify Quadrilaterals Example 3:Find a Missing Angle Measure

3. Main Idea/Vocabulary Classify quadrilaterals and find missing angle measures in quadrilaterals. quadrilateral rectangle square parallelogram rhombus trapezoid

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5. Example 1 Find a Missing Angle Measure Find the value of x in the quadrilateral shown. Since the sum of the angle measures in a quadrilateral is 360°, x + 50 + 130 + 50 = 360.

6. Example 1 Find a Missing Angle Measure 130 + 230 = 360You know that 130 + 230 = 360. Answer: So, the value of x is 130. x + 50 + 130 + n50 = 360Write the equation. x + 230 = 360Add 50, 130, and 50. THINK What measure added to 230 equals 360?

7. 1.A 2.B 3.C 4.D Example 1 A.70 B.80 C.90 D.110 Find the value of x in the quadrilateral shown.

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9. Example 2 RUGS Classify the quadrilateral of each rug below. Answer: The first rug is a parallelogram. The second rug is a square. Classify Quadrilaterals

10. 1.A 2.B 3.C 4.D Example 2 A.rectangle B.square C.rhombus D.trapezoid Classify the quadrilateral at the right.

11. Example 3 SHORT RESPONSE What is the value of x in the quadrilateral below? Find a Missing Angle Measure Read the Item You need to find the value of x. Solve the Item Since the sum of the angle measures in a quadrilateral is 360°, x + 90 + 90 + 73 = 360.

12. Example 3 Answer: The value of x is 107. x + 253 = 360Add 90, 90, and 73. THINK What measure added to 253 equals 360? 107 + 253 = 360You know that 107 + 253 = 360. x + 90 + 90 + 73 = 360Write the equation. Check 107 + 90 + 90 + 73 = 360 Find a Missing Angle Measure

13. 1.A 2.B 3.C 4.D Example 3 A.60 B.80 C.90 D.95 What is the value of x in the quadrilateral below?

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15. Resources Five-Minute Check (over Lesson 9–4) Image Bank Math Tools Estimating Angles Angles in Triangles

16. 1.A 2.B 3.C Five Minute Check 1 A.acute B.right C.obtuse Classify the triangle as acute, right, or obtuse. (over Lesson 9-4)

17. 1.A 2.B 3.C Five Minute Check 2 A.acute B.right C.obtuse Classify the triangle as acute, right, or obtuse. (over Lesson 9-4)

18. 1.A 2.B 3.C 4.D Five Minute Check 3 A.25 B.35 C.45 D.55 Find the value of x in the triangle. (over Lesson 9-4)

19. 1.A 2.B 3.C 4.D Five Minute Check 4 A.70 B.75 C.80 D.95 Find the value of x in the triangle. (over Lesson 9-4)

20. 1.A 2.B 3.C Five Minute Check 5 A.scalene B.isosceles C.equilateral A triangle has sides measuring 6 centimeters, 6 centimeters, and 9 centimeters. Classify the triangle by its sides. (over Lesson 9-4)

21. 1.A 2.B 3.C 4.D Five Minute Check 6 A.12° B.52° C.72° D.92° A triangle has angles measuring 38° and 70°. What is the measure of the triangle’s third angle? (over Lesson 9-4)

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