Number of integral values of k for which the equation 4 cos-1-x=k has exactly two solutions is

4cos-1-x=k⇒cos-1-x=k4                             1The graph of y=cos-1-x is as shown in the following figureClearly from the figure equation (1) has two solutions if line           y=k4  intersect  the  graph   between   π2   and  π.∴       π2