a. Show that cos 3 sin can be written in the form R cos ( ), with R > 0 and

a. Show that cos θ − √3 sin θ can be written in the form R cos (θ − α), with R > 0 and 0 < α / π/2.

b. Hence sketch the graph of y = cos θ − √3 sin θ, 0 < α < 2π, giving the coordinates of points of intersection with the axes.