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Published byCaitlin Barrett Modified over 9 years ago
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Then/Now You solved equations by adding or subtracting. (Lesson 4–3) Find the missing angle measure of a triangle. Classify triangles by properties and attributes.
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Vocabulary line segment triangle vertex congruent
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Concept A
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Example 1 Find Angle Measures 100 + 33 + x =180Substitution 133 + x=180Simplify. 133 – 133 + x=180 – 133 Subtract 133 from each side. x=47Simplify. Answer: x is 47, so m F = 47°. Find the value of x in ΔDEF. Write an equation.
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Example 1 A.57 B.123 C.139 D.303 Find the value of x in ΔMNO.
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Example 2 Use Algebra to Find Angle Measures ALGEBRA The measures of the angles of a triangle are 2x, x + 25, and x – 5. What are the measures of the angles? 4x +20 = 180Combine like terms. x = 40Simplify. 2x + (x +25) + (x + -5) = 180Write the equation. The sum of the angle measures is 180. - 20 -20 Subtract. Divide each side by 4. 4x = 160 Simplify.
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Example 2 Answer: The measures of the angles are 80°, 65°, and 35°. Substitute 40 for x in each expression. 2x = 2(40) = 80 x + 25 = 40 + 25 = 65 x - 5 = 40 - 5 = 35 Use Algebra to Find Angle Measures
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Concept B
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Concept C
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Concept D
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Example 4 Classify Triangles A. Classify the triangle below by its angles and by its sides. Answer: The triangle is an obtuse scalene triangle. Angles: The triangle has an obtuse angle. Sides: The triangle has no congruent sides.
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Example 4 Classify Triangles B. Classify the triangle by its angles and by its sides. Answer: The triangle is a right isosceles triangle. Angles: The triangle has a right angle. Sides: The triangle has two congruent sides.
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Example 4 CYP A A.right scalene B.obtuse scalene C.obtuse isoceles D.acute equilateral A. Classify the triangle by its angles and by its sides.
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Example 4 CYP B A.right isoceles B.obtuse isoceles C.obtuse scalene D.acute equilateral B. Classify the triangle by its angles and by its sides.
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Concept D
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