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4.1 notes

  1. 1. 4.1 Triangles & Angles October 10, 2011 Chapter 4: Congruent Triangles Activity: Find the sum of the measures of the angles. Materials: Paper, Ruler & Scissors Draw 2 different sized triangles with one of the sides extended. Label the 4 angles. Cut out the triangles. A W X Y Z B C D 1st Triangle: Tear off the three corners. Place them next to each other on the extended line. Make a conjecture about the sum of the measures of interior <s 2nd Triangle: Tear off corners that arent next to the exterior <s. Use them to fill the exterior <. Make a conjecture about the relationship between the measure of an exterior < and the nonadjacent interior <s. Conclusions: The sum of the measures of the interior <s of a triangle = 180. The measure of the exterior angle of a triangle the sum of the 2 nonadjacent interior <s.HW pg. 221 #8­18 evens, 21­26, 32 & 36 1
  2. 2. 4.1 Triangles & Angles October 10, 2011 4­1 Triangle Sum Properties Objectives: To understand the sum of the measures of the angles of a  triangle. Classify Triangles by Sides Scalene Isosceles Equilateral  Classify Triangles by Angles Acute Right Obtuse EquiangularHW pg. 221 #8­18 evens, 21­26, 32 & 36 2
  3. 3. 4.1 Triangles & Angles October 10, 2011 Triangle Sum Theorem The sum of the measures of the angles in every triangle is  _____. xo x = ______ 54o 39o no n = ______ 135o 30oHW pg. 221 #8­18 evens, 21­26, 32 & 36 3
  4. 4. 4.1 Triangles & Angles October 10, 2011 Exterior Angle Theorem The measure of an exterior < of a triangle = the sum of the measures of the 2  nonadjacent interior <s. Nonadjacent Interior Exterior Angles Angle 2 1 3 Corollary to the Triangle Sum Theorem The acute angles of a right triangle are complementary.  A <A + <C = 90 B CHW pg. 221 #8­18 evens, 21­26, 32 & 36 4
  5. 5. 4.1 Triangles & Angles October 10, 2011 Find the measure of each numbered angle in the figure. 3 2 50o 1 120o 4 5 o o 78 56 109o 95o 1 2 3 o 33 24oHW pg. 221 #8­18 evens, 21­26, 32 & 36 5
  6. 6. 4.1 Triangles & Angles October 10, 2011 HW pg. 221 #8­18 evens,  21­26, 32 & 36HW pg. 221 #8­18 evens, 21­26, 32 & 36 6

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