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Similarity


              a Side-Side-Side  (SSS)  similarity
                                                          Example 3�5
              theorem.
           3.  Two    corresponding     sides   are    For each pair of triangles in the
              proportional   and    one   pair   of    following  figures,  determine  whether
              corresponding angles (formed by these    they are similar  or not. Indicate  the
          FOR ONLINE READING ONLY
              sides) are equal is described by the Side-  similarity theorem used to support your
              Angle-Side (SAS) similarity theorem.     argument.


                                                       (a)
           Angle-Angle (AA) similarity theorem                                                       Mathematics for Secondary Schools
           The  AA  similarity  theorem  states that,
           two  triangles  are  similar  if  two  pairs  of
           corresponding  angles  are  equal.  This
           implies  that,  if two pairs of angles are
           equal, the third pair of angles will also be
           equal as described in Figure 3.3.






                                                       (b)






            Figure 3�3: Similar triangles by the Angle-
                         Angle  theorem

           In Figure 3.3, it can be observed that,
                             ˆ
              ˆ
                      ˆ
                                     ˆ
            BAC  =   QPR,  ACB  =   PRQ                (c)
                            ˆ
                    ˆ
           Thus, ABC  =    PQR (third pairs of angles
           of triangles)


           Therefore,  ABC ~ PQR     and


            AB  =  BC  =  AC .
            PQ    QR    PR                              Solution

                                                        (a)  Required to prove that:
                                                               OUL ~ MUO   ,


                                                    45
           Student's Book Form Two


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