Students approached this question in two ways, namely rearranging for x (x = 2sin(y) ) or applying the chain rule using the formula sheet. In the former case most students

got to the correct form of the final question, but there was often an error in the transposition of the 2 (e.g. getting x =sin(y/2)), which carried and caused errors in the coefficients of the results. There were also a few cases where students also did not finish the question by substituting the formula for cos(y) back in to get the result in terms of x.For the students who used the formula sheet to differentiate arcsin(x/2), several students did not apply the chain rule to compensate for the x/2, or forgot to substitute x/2 back after the formula (i.e.their "u' was just relabelled to x).