I am trying to isolate y:

I have:

ln sqrt(1+y^2) = t + (t^2)/2 + A

exponeniate:

sqrt( 1 + y^2 ) = exp( t + (t^2)/2 + A )

y^2 = ( exp( t + (t^2)/2 + A ) )^2 - 1

Let: B = exp(A)

y = Sqrt( ( B * exp(t) * exp(t^2)/2) )^2 - 1)

Let: C = B^2

y = Sqrt( C * ( exp(t) * exp (t^2)/2 ) )^2 - 1)

Correct?