Prove Theorem 1.3(a).

Lecture 4: Recall: a trace is the intersection of the surface with one of the coordinate planes x=k, y=k and z=k. Traces will be used to graph quadratic surfaces in 3-dimensional space. How to graph in 3-D. Step 1: Identify the general traces x=k g=k, z=k and select one family that is easy to draw.