1. The problem statement, all variables and given/known data Limit of (arcsen(2x)-2arcsen(x))/x^3 as x->0 2. Relevant equations arsen(x)'=1/Sqrt(1-x^2) 3. The attempt at a solution It's an 0/0 indeterminancy, to solve it, I had to use L'hopital's rule once simplify de expression, multiplying by the conjugate root. Is there an easier way?