In the chapter on matrices we studied that the area of a triangle in the plane with vertices $latex (x_1, y_1), (x_2, y_2), (x_3, y_3)$ can be determined by calculating a determinant with row i consisting of $latex x_i \,y_i \,1$ for i between 1 and 3. Then take the absolute value it and divide by 2. If the value turns out to be 0 then the points must have been collinear. I've posted a Sage Interact to generate problems to use during the lesson since the book doesn't have enough extra problems. It's posted on the Sage in the Classroom page and you can see the output above.

In a recent post, I mentioned an audio interview with Simon Singh talking about his book ‘The Simpsons and Their Mathematical Secrets’. The NY Times had a piece on this today, too: "Examining the Square Root of D’oh!" which provides even more information: the creators have included, over the years, "J. Stewart Burns, who has a master’s degree in math from Harvard; David X. Cohen (master’s in computer science, University of California, Berkeley); and Ken Keeler (Ph.D. in applied math, Harvard). Most astonishing is Jeff Westbrook (Ph.D., computer science, Princeton), who was an associate professor at Yale before he joined the team.". That's got to be the smartest creative team in television history.

The Sagemath Twitter feed tweets that Sagemath Cloud is now capable of producing graphs using Plotly. As if you didn't have enough reasons to use Sage; now you've got one more.