y=sin^-1[2ax{√1-a^2x^2] diff. this sir problem in starting the solution

Dear Student,
:- For this question
         At first assume , Sin A= ax,
         So, Cos A= √1-a^2x^2
         Putting the  values in the given question we get ,
         Y= Sin^-1 [ 2 Sin A Cos A]
           = Sin^-1 [ Sin 2A]
           = 2A
       A= Sin^-1 ax
      So, y = 2 Sin^-1 ax.
       Dy/dx = 2a/ √1-a^2x^2