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I need help with understanding the problem. The coding isn't really the problem rather the math part. I don't understand what a delta test method that tells me determinant of a 3x3 matrix is supposed to help determine if an array of vertices of a simple polygon is convex or not. What does the determinant of 3x3 matrix mean? how does the determinant tell me the orientation of polygon? How can this help me determine if array of vertices of simple polygon is convex or not? I tried to implement using the gift wrapping method but the teacher said that it was too complicated for the class and just said to use the delta test to help. This kind of seems like duplicate of a few question but I still don't answer the solutions given:

What is the real meaning of the determinant of a matrix?

https://stackoverflow.com/questions/25830932/how-to-find-if-two-line-segments-intersect-or-not-in-java

but as a novice in these fields any help will be appreciated :)

TaeCoda
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  • I tried to ask in the stack exchange programming but it was held. I just wanted to understand the question and the math parts. – TaeCoda Jan 08 '19 at 01:32
  • "I need help with understanding the problem. The coding isn't really the problem rather the math part." What problem are you referring to? I can't tell. – littleO Jan 08 '19 at 01:35
  • https://stackoverflow.com/questions/25830932/how-to-find-if-two-line-segments-intersect-or-not-in-java is the same "assignment" but I am working on trying to use the delta test (in the same link) to help determine if a given list of vertices is convex or not. – TaeCoda Jan 08 '19 at 01:37
  • Oh I see, I didn't realize that the second question you linked to was specifically the problem you're working on. – littleO Jan 08 '19 at 01:39
  • sorry. I am not very good at articulating my problems with English very well. – TaeCoda Jan 08 '19 at 01:47
  • @TaeCoda Look up cross product on wikipedia. I think that will help you a lot. – Rushabh Mehta Jan 08 '19 at 02:10
  • how would cross product help? I don't see the relationship between the delta test, convex polygon or not? @_@ – TaeCoda Jan 08 '19 at 02:21
  • The cross product is the determinant of a $3\times 3$ matrix. – Matt Samuel Jan 08 '19 at 02:28
  • i see. so then how does that cross product (determinant of 3x3 matrix) mean in terms of this problem? Does the cross product mean the given list of vertices is convex polygon? – TaeCoda Jan 08 '19 at 02:42
  • This may help – saulspatz Jan 08 '19 at 03:18

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