[ADMB Users] Using asin with df1b2variables

[dave fournier]

I don't think that my asin is "wrong".  There is an implicit limitation 
on the range of the function
which should be made explicit. asin(x) is much like sqrt(x) where 
sqrt(0) is well defined,
but its derivative is infinite.

Similarly asin(pi/2) and asin(-pi/2) are well defined but their 
derivatives are infinite.  For that
reason there is an implicit limitation  -pi/2<x<pi/2.

I think you will find that if your animal is moving straight north your 
function will blow up.