Exercise 8 Page 383

We are given a diagram representing a molecule of phosphorus pentachloride. In this exercise we want to name two planes that contain line $s.$ If two points lie on a plane, and we draw a line that contains both these points, the entire line will be contained in that plane. From the given diagram, we can see that, if our planes of choice contain points $G$ and $I,$ they will also contain the line $s.$

We can choose point $J$ as the third points needed to define our first plane. We have marked this on the graph. Since this plane contains points $G,$ $I$ and $J,$ we can name it $GIJ.$ For the second plane, we can instead choose $L$ as the third point. This defines the second plane to be $GIL,$ since it contains points $G,$ $I,$ and $L.$

We have found two planes containing points $G$ and $I,$ plane $GIJ,$ and plane $GIL.$ Line $s$ contains these points, so planes $GIJ$ and $GIL$ contain line $s.$