For 0<x<2π, a curve is defined by y=xsinxtanx.
(i) Find dxdy and simplify your answer as far as possible.
(ii) Determine the value of dxdy at x=4π.
(iii) Using your result from part (ii), find the acute angle made by the tangent to the curve with the positive direction of the x-axis at the point where x=4π.