CD=b(sin(A))=a(sin(B))

I can write

Now,

AD=b.cos(A) and BD=a.cos(B)

Now its given That CD.CD=AD.BD

I get

and A+B=90.

which means C=90

Now as we know that sin of any angle is less than or equal to 1.

Now 2sin(A)cos(A)<=1

         2sin(A)sin(B)<=1          (since C=90, cos(A)=sin(B))

        i.e