Express 3cosθ + 4sinθ in the form Rcos(θ-α), where R > 0 and 0 < α < 1/2π.
Hence find the range of the function f(θ), where f(θ) = 7+3 cosθ + 4sinθ for
0 ≤ θ ≤ 2π.
Write down the greatest possible value of 1/(7+3cosθ+4sinθ).​