A pendulum is swinging next to a wall. The distance from the bob of the pendulum to the wall varies in a periodic way that can be modeled by a trigonometric function. The modeling function has period of 0.8 seconds, amplitude of 6, and midline H = 15. At time t = 0.2, the bob is at its midline, moving towards the wall. Find the formula of the trigonometric function that models the distance H between the bob and the wall after t seconds. Define the function using radians.