For the curve y=xcosx, consider the interval 0<x<2π.
a. (i) Obtain dxdy.
b. (ii) Determine all values of x in the given interval for which the tangent to the curve is horizontal.
c. (iii) For each value of x found in part (ii), state whether the curve is rising or falling immediately to the right of that point, giving reasons based on the derivative.