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Triangles and Angles

Triangles and Angles. Classifying Triangles. Line segments are congruent if they have the same length; shown by the number of marks on the line segment One way to classify triangles is by the number of congruent sides they have. Congruent. Congruent. Classifying Triangles.

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Triangles and Angles

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  1. Triangles and Angles

  2. Classifying Triangles • Line segments are congruent if they have the same length; shown by the number of marks on the line segment • One way to classify triangles is by the number of congruent sides they have Congruent Congruent

  3. Classifying Triangles • Scalene Triangles have no congruent sides • Isosceles Triangles have two congruent sides • Equilateral Triangles have three congruent sides

  4. Classifying Triangles • Another way to classify triangles is by the measure of their angles • Acute Triangles have three acute angles • Obtuse Triangles have one obtuse angle • Right Triangles have one right angle

  5. Classifying Triangles Checkpoint • Classify each triangle by its sides and it’s angles: Angle: Angle: Angle: Side: Side: Side: Acute Equilateral Obtuse Scalene Right Isosceles

  6. Triangle Mini-Lab • Materials Needed: • Pencil • Ruler (share with a neighbor) • Scissors (share with a neighbor)

  7. Triangle Mini-Lab • Using a ruler and pencil, draw any large triangle and cut it out with scissors. • Individually label each angle 1, 2, and 3. • Tear off (do NOT cut) a large section of each angle and arrange so each vertex is touching and each angle is adjacent to the next.

  8. Triangle Mini-Lab • What type of angle did the three angles form when placed together? • What is the measure of this angle? • Let’s confirm…. A straight angle 180º

  9. Interior Angles of a Triangle The sum of the measures of the angles of a triangle is 180

  10. Finding The Measures of Angles Checkpoint Find the measure of each angle then classify the triangle by its angles: m a = 46º, m b = 42º, m c = Classify: xº + 46º + 42º = 180º xº + 88º = 180º x = 92º 92º Obtuse

  11. Finding The Measures of Angles Checkpoint Find the measure of each angle then classify the triangle by its angles: m a = 3xº, m b = 2xº, m c = xº Classify: xº + 2xº + 3xº = 180º 6xº= 180º x = 30º 3(30º) = 90º 2(30º) = 60º x = 30º Right

  12. Finding The Measures of Angles Checkpoint Find the measure of each angle then classify the triangle by its angles: m a = 4xº, m b = 3xº, m c = 2xº Classify: 4xº + 3xº + 2xº = 180º 9xº = 180º x = 20º 4(20º) = 80º 3(20º) = 60º 2(20º) = 40º Acute

  13. Homework • Skill 6: Triangles (both sides) • 6-2 Practice Skills: Triangles and Angles (both sides) • Due Tomorrow!

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