Properties of Triangles 
                            Properties of Triangles 
  Using the symbols describing shapes answer the following questions:
               b
                                                             o
                                                           45
             o    a
           36                     c                                   d
       Isosceles triangle      Equilateral triangle     Right-angled triangle
    Two angles are equal       all angles are equal
      a = 36o                    c = 180 ÷ 3 = 60o      d = 180 – (45 + 90)
      b = 180 – (2 × 36)                                         = 45o
             = 108o
                               Properties of Triangles 
                               Properties of Triangles 
       Example                          Made up of 2 isosceles triangles
                               q         o            p = 38o
                                       36 s
                                                      q = 180 – (2 × 38) = 104o
                             p
                              r
                             o                    o
        56 + (r + s) =  180                     56
              (r + s) =  180 – 56 = 124
Because                  r = s
                          r = s = 124 ÷ 2 = 62o
                                 Properties of Triangles 
                                 Properties of Triangles 
    Now do these:
                                                   Equilateral triangle  h = i
    a = 64o                                                              h + i = 180 - 90
                                  c = d              e = f = g = 60o     h + i = 90
    b = 180 – (2 ×64o ) = 52o    c + d = 180 - 72                                  o
                                                                         c = d = 45
                                 c + d = 108
                                           o
                                 c = d = 54
     p = 50o
     q = 180 – (2 ×50o ) = 80o
               o
     r = q = 80  vertically opposite angles are equal
                                  o
 Therefore :        s = t = p = 50
              Properties of Triangles 
              Properties of Triangles 
                             p = q = r = 60o
     e = f = g = 60o
   d = 180 – 60 = 120o     s = t = 180 - 43 = 68.5o
    e + 18 = a = 60            2
  external angle = sum of opposite internal angles
    e = 60 – 18 = 42o
    
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