This lesson introduces another method for multiplying two vectors together: the cross product. The cross product produces a vector, not a number (as in the case of the dot product). We’ll spend the lesson exploring this distinction and what insights the cross product yields.
In Module 1 we’ll define the cross product and discover that, like the dot product, it can be used to calculate the angle between two vectors. Moreover, we’ll learn that the vector the cross product produces is orthogonal to the two vectors being “crossed.”
In Module 2 we’ll use that orthogonality fact to derive the equation of a plane in 3D.
Finally, in Module 3 we’ll re-interpret our results on the equations of planes to extract the general equation of a line in 3D.
Work through the lesson notes below, consulting the videos below it when you get to the "See Class Notes" boxes. For your records, the annotated lesson notes are below the videos. Some tips for you as you work through these resources:
I recommend using Cornell Notes (or a modification of it; see this video starting at the 1:05 mark) to take notes on the lesson and the videos. This note-taking method balances detail with big-picture thinking to help you summarize and retain what you are learning. See this other video for additional note-taking techniques you might want to experiment with.
If you are currently enrolled in this course with me, submit the written reflections Google Form I have emailed you after working through the lesson notes and videos. Some tips:
Submit substantive, but concise, answers to each question; you will be doing the future you a big favor by taking time now to accurately and succinctly summarize what you have learned from the lesson.
Send yourself a copy of your reflections; they will come in handy later when you start preparing for quizzes and other assessments.
If you are not currently enrolled in this course with me, those written reflections ask three reflective questions designed to help you retain what you've learned and pinpoint any remaining areas of confusion. Those questions are:
Please summarize the main mathematical takeaways from the lesson notes.
What was the most interesting part of what you learned, and why?
What, if anything, do you still find confusing?
Work through the practice problems suggested below to see how much of this lesson you've understood.