Question

My question is with respect to PS4-2B-2b. I don't understand the intuition behind it. In particular, how can a line lie on both the cone and the tangent plane at a point on it. By definition a t-plane, and all lines on it, would not touch the cone at any other point near the point of tangency. Therefore, said line on a t-plane could not be completely contained within the cone as well. If someone could explain essentially, "what's going on" in this question, it would be appreciated. I apologize for the vagueness of the question. I'll attach screenshots of the questions and answer

Answer 1

Here are the screenshot. Thanks in advance.

Answer 2

**By definition a t-plane, and all lines on it, would not touch the cone at any other point near the point of tangency. ***

That is not necessarily true. In the extreme case of a "tangent plane" to a point on a plane, the tangent plane coincides with the given plane at all points.

Or for a cylinder, a tangent plane to the cylinder would share a line