2020-02-25 10:06:58 +0200 received badge ● Famous Question (source) 2017-09-04 22:31:01 +0200 received badge ● Notable Question (source) 2013-07-03 04:41:32 +0200 received badge ● Popular Question (source) 2012-01-17 06:33:08 +0200 received badge ● Student (source) 2012-01-16 15:33:58 +0200 marked best answer Contour Plots and Points The point is there -- it's simply lurking behind the contour plot. Or, in matplotlib jargon (one of the plotting packages Sage uses is called matplotlib), it doesn't have a higher zorder. The zorder is the layer level, where the layers are drawn from lower to higher. I can never remember what zorders different things default to, but it's usually easily changed manually: var('x,y') f(x,y)=sin(x)*cos(y) G = contour_plot(f(x,y),(x,-3,3),(y,-3,3),contours=20,plot_points=100) G += point((1,1), size=100,zorder=2) G.show()  produces 2012-01-16 15:33:58 +0200 received badge ● Scholar (source) 2012-01-16 10:03:36 +0200 answered a question Contour Plots and Points Thanks. Just to be certain, why does subsequently plotting a line without a zorder not put that line behind the contour plot as well? 2012-01-15 21:41:59 +0200 received badge ● Editor (source) 2012-01-15 21:39:31 +0200 asked a question Contour Plots and Points Why can I not have a single point on a contour plot? var('x,y') f(x,y)=sin(x)*cos(y) G = contour_plot(f(x,y),(x,-3,3),(y,-3,3),contours=20,plot_points=100) G += point((1,1), size=100) G.show()  does not display the point. I can add a line (for example) G += line(((1.5,1),(1.5,0)))  and that line shows up but not the point. Thanks. JT 2011-09-12 15:51:44 +0200 received badge ● Supporter (source) 2011-08-19 12:29:38 +0200 received badge ● Teacher (source) 2011-08-19 11:36:30 +0200 answered a question vector calc There are numerous worksheets scattered about that deal with multivariate calculus but I don't know of any organized collection--yet. This is something that is being considered and hopefully will be available next time you teach this course. I have published a number of short worksheets at Mississippi College and you are welcome to give any of them a try. Some of these are being designed to work from within WeBWorK and so may not have very much of a descriptive component.