1.∆ ABC and ∆ DBC are two isosceles triangles on the same base BC and vertices A  and D are on the same side of BC (see Fig). If AD is extended to intersect BC at P, show that 
   
                
                  Consider   and   
,
(i)    is common side in both the triangles.
(ii)   (This is obtained from the c.p.c.t. as proved in the previous part.)
(iii)           (Isosceles triangles)
Thus by SAS axiom, we can conclude that :