A two-dimensional map also called the Taylor-Greene-Chirikov map in some of the older literature and defined by I_(n + 1) | = | I_n + K sin θ_n θ_(n + 1) | = | θ_n + I_(n + 1) | = | I_n + θ_n + K sin θ_n, where I and θ are computed mod 2π and K is a positive constant. Surfaces of section for various values of the constant K are illustrated above. An analytic estimate of the width of the chaotic zone finds δ I = B e^(-A K^(-1/2)).