Study of the sine function on one complete revolution.
(i) Using equal intervals of 6π on the x-axis, plot and join the points to obtain a smooth sketch of the graph y=sinx for 0≤x≤2π.
(ii) With the help of your sketch, determine the set of x values in [0,2π] for which sinx≥21.
(iii) Express your answer from part (ii) in the form of one or more closed intervals.