Property of circle regarding chaord and tangent

On the screen, we see a circle with center A and T is a point on its circumference. A tangent is drawn at point T and there is a point P outside the circle, lying on this tangent. From this point P a line is drawn (as shown in the figure) which cuts the circle at points C and D. Let us move the points A, D, P and T and observe how the lengths of PC, DP and PT get changed.