Points of tangency also act as endpoints of secant lines true or false

False. A secant line intersects a circle in exactly two places. A tangent line touches the circumference of the circle in exactly one place all the time. This would only be true if a secant ran through the two points of tangency created by 2 lines. I have included a diagram to show you what that means.

AB is a secant. It runs through the two points of tangency (also called A and B). That is a very special secant and the only one that will do what it does for the external point where the tangents start from. If you draw another secant it will not do what this one does unless the 2 secants are one on top of the other.