The curve C has parametric equations x = sin t, y = cos 2t + 1, 0 < t < 2. Given that the line

The curve C has parametric equations x = sin t, y = cos 2t + 1, 0 < t < 2π. Given that the line y = k, where k is a constant, intersects the curve, 

a. Show that 0 < k < 2 

b. Show that if the line y = k is a tangent to the curve, then k = 2.