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20160525 22:45:37 0600  asked a question  Getting convex hull of a set of points and plotting the polygon I'm using sagemath cloud. I'm trying to get the convex hull of a finite set of points, then plotting the polygon. If I just plot the polygon with the vertices directly, I don't get the vertices in the right order to make up a convex polygon (plots edges joining the wrong points). Then I found out about cyclic_sort_vertices_2d which I thought would sort the vertices into the right order, but that's giving me errors. I don't understand the meaning of the errors. Appreciate any help. here's the relevant code: And I have this import line at the top of my code for cyclic sort: Here's my output: And errors: 
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20151107 18:56:35 0600  commented answer  solving simultaneous equations Thanks! I see now. 
20151107 12:21:00 0600  asked a question  solving simultaneous equations Here's my code: And here's my output: I'm looking for any solutions, exact or numerical approximation. Appreciate any help. I can solve the problem by hand, but obviously that's not the point here. I'm trying to find out what I'm doing wrong and learn to use sagemath cloud properly. 
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20151107 12:13:45 0600  commented answer  Having trouble solving simultaneous questions It is not letting me upvote. I will accept the answer though. 
20151107 10:07:58 0600  commented answer  Having trouble solving simultaneous questions Seems like replacing x with x1 helped a little, but it's not solving the system of equations. 
20151107 10:06:11 0600  commented answer  Having trouble solving simultaneous questions Thanks. I tried that and here's what I get:
HEre's the output: x1 + x2 : 3, (x1  1)(x1  2) + (y1  3)(y1  4) : 0, (x2  1)(x2  2) + (y2  3)(y2  4) : 0, y1 + y2 : 7, 
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20151107 07:19:22 0600  asked a question  Having trouble solving simultaneous questions I'm trying to use sagemath cloud to solve simultaneous equations, but I'm having trouble. Can you please look at the code below and see what I'm doing wrong. sagemath cloud gives the following error: Error in lines 77 Traceback (most recent call last): File "/projects/sage/sage6.9/local/lib/python2.7/sitepackages/smc_sagews/sage_server.py", line 905, in execute exec compile(block+'\n', '', 'single') in namespace, locals File "", line 1, in <module> KeyError: x My code:
