minthao_2011
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 Dec 14 comment How to get the correct answer of this expression with Minimize? @JimBaldwin I knew this command and I did that. Dec 14 comment How to get the correct answer of this expression with Minimize? @belisariushassettled Thank you. I tried. Can I get the correc answer? Feb 9 comment Calculate area under a polyline @MichaelE2 If I change the code into tmp = {{0, 0}, {1, 1}, {2, 1}, {3, 2}, {1, 6}}; plot = ListLinePlot[tmp, Filling -> Axis]; Area@DiscretizeGraphics[plot] I got the answer is 8. My maple has the same result. But your code is 6. I don't understand why? Dec 23 comment How to select a list from a list? I am sorry. I did. Dec 23 comment How to select a list from a list? If each element contains four points, for example, {{-5, -1, -1}, {-5, -1, 3}, {-5, 4, -2}, {3, -1, -5}}. I tried Select[nonright, (12 == Length[Union @@@ #] &)] it does not correct. Please help me. Dec 22 comment How to select a list from a list? Thank you very much. Dec 22 comment How to select a list from a list? @ belisarius In line Select[lst, ( 9 == Length[Union @@ #] &)] If I want 9 numbers different from 0. How can I select? Dec 21 comment How to select a list from a list? Yes. I will edit my question. Dec 21 comment How to select a list from a list? You understand me. Thank you very much. Jul 17 comment Is this a bug in FunctionDomain (V.10)? Mclure First, thanks to your answer. I think, we want to find the domain of the given function, we must solve the inequality x^3+1<>0. Jun 24 comment How do I calculate the area of a polygon given its coordinates? Thank you very much. Jun 24 comment How do I calculate the area of a polygon given its coordinates? when I tried pts = {{5, 2}, {4, 1}, {1, 3}}; GraphicsMeshMeshInit[]; PolygonArea[pts] I got -2.5. I don't understand. Jun 24 comment How do I obtain the enclosed area of this particular parametric plot? I tried pts = {{5, 2}, {4, 1}, {1, 3}}; GraphicsMeshMeshInit[]; PolygonArea[pts] but I received -2.5 Jun 23 comment How can I get the exact real solution of this equation? Jun 23 comment How can I get the exact real solution of this equation? I am a teacher. When I teach for my students, in this case, when we solve by hand, we always conclude the given solution has only real solution (solve in real domain). Am I wrong? Jun 23 comment How can I get the exact real solution of this equation? Thank you very much for your answers and your helps. Jun 23 comment How can I get the exact real solution of this equation? Perhaps about my English, therefore my question is not clearly. My question is "How many solutions when I solve the equation Sqrt[x] + Sqrt[1 - x^2] == Sqrt[2 - 3 x - 4 x^2] in the real domain? Jun 23 comment How can I get the exact real solution of this equation? I have just online. Thank you four your answer. Jun 23 comment How can I get the exact real solution of this equation? I used Solve[Sqrt[x] + Sqrt[1 - x^2] == Sqrt[2 - 3 x - 4 x^2], x, Reals] // ToRadicals, then I got one real solution. Jun 23 comment How can I get the exact real solution of this equation? @MichaelE2 I use Solve[Sqrt[x] + Sqrt[1 - x^2] == Sqrt[2 - 3 x - 4 x^2], x, Reals] // ToRadicals and received one real solution. Thank you.