question_answer

    If two isosceles triangles have a common base prove that the line joining their vertices bisects the common base at right angle.  

Answer:

    Given Two and with common        base andand To prove and Proof In and we have                   [given]                   [given]            [common]                   (1)  [by SSS congruence]                                  [by CPCT]                       [by CPCT](1/2) Now, in and                                        [given]          [proved above]                                [common] [by SAS congruence]                                 [by CPCT]                     [by CPCT]?(i)(1/2) Also,   [linear pair]..(ii) From Eqs. (i) and (ii), we have                              (1/2)