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Transparency 4. Click the mouse button or press the Space Bar to display the answers. Splash Screen. Example 4-4b. Objective. Identify and classify triangles. Example 4-4b. Vocabulary. Triangle. A polygon that has three sides and three angles. Example 4-4b. Vocabulary. Acute triangle.

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  1. Transparency 4 Click the mouse button or press the Space Bar to display the answers.

  2. Splash Screen

  3. Example 4-4b Objective Identify and classify triangles

  4. Example 4-4b Vocabulary Triangle A polygon that has three sides and three angles

  5. Example 4-4b Vocabulary Acute triangle A triangle having three acute angles

  6. Example 4-4b Vocabulary Right triangle A triangle having one right angle

  7. Example 4-4b Vocabulary Obtuse triangle A triangle having one obtuse angle

  8. Example 4-4b Vocabulary Congruent segments Sides of a triangle having the same length

  9. Example 4-4b Vocabulary Scalene triangle A triangle having no congruent sides

  10. Example 4-4b Vocabulary Isosceles triangle A triangle having at least two congruent sides

  11. Example 4-4b Vocabulary Equilateral triangle A triangle having three congruent sides

  12. Lesson 4 Contents Example 1Find Angle Measures of Triangles Example 2Find a Missing Measure Example 3Classify Triangles Example 4Classify Triangles

  13. Example 4-1a PLANES An airplane has wings that are shaped like triangles. Find the missing measure. x0 + 470 = 1800 + 1120 The sum of the measures is 1800 Add angles together Remember: sum = 1800 1/4

  14. Example 4-1a PLANES An airplane has wings that are shaped like triangles. Find the missing measure. Bring down x0 x0 + 470 = 1800 + 1120 Combine “like” terms = 1800 x0 + 1590 Bring down = 1800 Ask “what is being done to the variable?” The variable is being added by 1590 Do the inverse on both sides of the equal sign 1/4

  15. Example 4-1a PLANES An airplane has wings that are shaped like triangles. Find the missing measure. Bring down x0 + 1590 Subtract 1590 x0 + 470 = 1800 + 1120 Bring down = 1800 = 1800 x0 + 1590 - 1590 = 1800 x0 + 1590 - 1590 Subtract 1590 x0 = + 00 Bring down x0 Combine “like” terms Bring down = 1/4

  16. Example 4-1a PLANES An airplane has wings that are shaped like triangles. Find the missing measure. Combine “like” terms x0 + 470 = 1800 + 1120 Use the Identify Property to add x0 + 00 = 1800 x0 + 1590 - 1590 = 1800 x0 + 1590 - 1590 x0 = + 00 210 Answer: x = 210 1/4

  17. Example 4-1b SEWINGA piece of fabric is shaped like a triangle. Find the missing measure. x Answer: x = 49 1/4

  18. ALGEBRAFind mA in ABC if mAmB and mC 80. Example 4-2a x Draw the triangle Define mA as x mA  mB 2/4

  19. ALGEBRAFind mA in ABC if mAmB and mC 80. Example 4-2a x 2 Since mA is x and m   mB then B can also be x x + x = 2x The sum of the measures is 1800 2/4

  20. ALGEBRAFind mA in ABC if mAmB and mC 80. Example 4-2a x 2 + 800 = 1800 Add 800 for the mC Put the = 1800 since this is the sum Solve for the unknown 2/4

  21. ALGEBRAFind mA in ABC if mAmB and mC 80. Example 4-2a Ask “what is being done to the variable term (2x)?” x 2 + 800 = 1800 - 800 2x + 800 - 800 The variable term is being added by 800 = 1800 Do the inverse on both sides of the equal sign Bring down 2x + 800 Subtract 800 Bring down = 1800 Subtract 800 2/4

  22. ALGEBRAFind mA in ABC if mAmB and mC 80. Example 4-2a Bring down 2x x 2 + 800 = 1800 Combine “like” terms - 800 2x + 800 - 800 = 1800 Bring down = 2x + 00 = 1000 Combine “like” terms 2x = 1000 Use the Identify Property to add 2x + 00 Ask “what is being done to the variable?” The variable is being multiplied by 2 2/4

  23. ALGEBRAFind mA in ABC if mAmB and mC 80. Example 4-2a Do the inverse on both sides of the equal sign x 2 + 800 = 1800 Bring down 2x = 1000 - 800 2x + 800 - 800 = 1800 Using the fraction bar, divide both sides by 2 2x + 00 = 1000 2x = 1000 Combine “like” terms 2x = 1000 2 2 Use the Identify Property to multiply 1  x 1  x = 500 Since you defined mA as x and x = 500 then mA = 500 x = 500 Answer: mA = 500 2/4

  24. ALGEBRAFind mJ in JKL if mJmK and mL 100. Draw the triangle then solve Example 4-2b Answer: mJ = 40 2/4

  25. Example 4-3a Classify the triangle by its angles and its sides. Obtuse All triangles have 3 names First, middle and last (just like you) First: classify angle One angle greater than 900 meets the definition of obtuse angle 3/4

  26. Example 4-3a Classify the triangle by its angles and its sides. Answer: Obtuse Isosceles Triangle Next, classify by sides 2 sides congruent meets the definition of isosceles All triangles have the last name as “triangle” 3/4

  27. Example 4-3b Classify the triangle by its angles and its sides. Answer: Right Scalene Triangle 3/4

  28. Example 4-4a Classify the triangle by its angles and its sides. Acute All triangles have 3 names First, middle and last (just like you) First: classify angle All angles are less than 900 meets the definition of acute angle 4/4

  29. Example 4-4a Classify the triangle by its angles and its sides. Answer: Acute Scalene Triangle Next, classify by sides No sides have a congruent symbol so meets the definition of scalene All triangles have the last name as “triangle” 4/4

  30. Example 4-4b * Classify the triangle by its angles and its sides. Answer: Acute Equilateral Triangle 4/4

  31. End of Lesson 4 Assignment

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