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Math Problem ...

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helpquestioncsharp
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  • E Ed Poore

    I know about MathWorld since I've got a copy of Mathematica, it's just I was being blind to the obvious yesterday, was feeling a bit more awake today but then sat down outside to read a book in the sun, big mistake.. Fell alseep.


    Formula 1 - Short for "F1 Racing" - named after the standard "help" key in Windows, it's a sport where participants desperately search through software help files trying to find actual documentation. It's tedious and somewhat cruel, most matches ending in a draw as no participant is able to find anything helpful. - Shog9

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    Paul Conrad
    wrote on last edited by
    #52

    Ed.Poore wrote:

    Mathematica

    I've always liked mathematica. Haven't worked with it in some time :sigh:

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    • P Paul Conrad

      Ed.Poore wrote:

      Mathematica

      I've always liked mathematica. Haven't worked with it in some time :sigh:

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      Ed Poore
      wrote on last edited by
      #53

      Havn't used it much but liked what I saw, but I find it's more fun to program your own stuff rather than getting Mathematica to do it. Mind you, you do get a sense of satisfaction when asking it to calculate Pi to 5,000,000 places, you think it's crashed and then you go off to supper, lo and behold when you come back it's done it.


      Formula 1 - Short for "F1 Racing" - named after the standard "help" key in Windows, it's a sport where participants desperately search through software help files trying to find actual documentation. It's tedious and somewhat cruel, most matches ending in a draw as no participant is able to find anything helpful. - Shog9

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      • R Ray Kinsella

        Hey Guys, I have a math issue, I know how you like brain teasers so I thought I would post it here, say I have two points ab & cd, how do I find the point 20% of distance between these two points on the same slope ? Regards Ray "Je Suis Mort De Rire" Blogging @ Keratoconus Watch

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        Lost User
        wrote on last edited by
        #54

        Ray Kinsella wrote:

        I have a math issue, I know how you like brain teasers so I thought I would post it here, say I have two points ab & cd, how do I find the point 20% of distance between these two points on the same slope ?

        Ask an Asian? Michael Martin Australia "I controlled my laughter and simple said "No,I am very busy,so I can't write any code for you". The moment they heard this all the smiling face turned into a sad looking face and one of them farted. So I had to leave the place as soon as possible." - Mr.Prakash 24/04/2004

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        • E Ed Poore

          Havn't used it much but liked what I saw, but I find it's more fun to program your own stuff rather than getting Mathematica to do it. Mind you, you do get a sense of satisfaction when asking it to calculate Pi to 5,000,000 places, you think it's crashed and then you go off to supper, lo and behold when you come back it's done it.


          Formula 1 - Short for "F1 Racing" - named after the standard "help" key in Windows, it's a sport where participants desperately search through software help files trying to find actual documentation. It's tedious and somewhat cruel, most matches ending in a draw as no participant is able to find anything helpful. - Shog9

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          Paul Conrad
          wrote on last edited by
          #55

          Ed.Poore wrote:

          it's more fun to program your own stuff rather than getting Mathematica to do it

          I agree. It's nice to use a tool like Mathematica to check the program to ensure it is working correctly :) Took a Graduate course called Super Visualization and tools like Mathematica and SciLab were quite useful.

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          • P Paul Conrad

            Ed.Poore wrote:

            it's more fun to program your own stuff rather than getting Mathematica to do it

            I agree. It's nice to use a tool like Mathematica to check the program to ensure it is working correctly :) Took a Graduate course called Super Visualization and tools like Mathematica and SciLab were quite useful.

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            Ed Poore
            wrote on last edited by
            #56

            What's your opinion of SciLab?


            Formula 1 - Short for "F1 Racing" - named after the standard "help" key in Windows, it's a sport where participants desperately search through software help files trying to find actual documentation. It's tedious and somewhat cruel, most matches ending in a draw as no participant is able to find anything helpful. - Shog9

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            • E Ed Poore

              What's your opinion of SciLab?


              Formula 1 - Short for "F1 Racing" - named after the standard "help" key in Windows, it's a sport where participants desperately search through software help files trying to find actual documentation. It's tedious and somewhat cruel, most matches ending in a draw as no participant is able to find anything helpful. - Shog9

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              Paul Conrad
              wrote on last edited by
              #57

              Ed.Poore wrote:

              What's your opinion of SciLab?

              It is pretty alright. Had to use it in conjunction with MuPad to solve a problem with wavelet transforms. PJC

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              • P Paul Conrad

                Ed.Poore wrote:

                What's your opinion of SciLab?

                It is pretty alright. Had to use it in conjunction with MuPad to solve a problem with wavelet transforms. PJC

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                Ed Poore
                wrote on last edited by
                #58

                :nod politely and pretend to understand: :-D


                Formula 1 - Short for "F1 Racing" - named after the standard "help" key in Windows, it's a sport where participants desperately search through software help files trying to find actual documentation. It's tedious and somewhat cruel, most matches ending in a draw as no participant is able to find anything helpful. - Shog9

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                • E Ed Poore

                  :nod politely and pretend to understand: :-D


                  Formula 1 - Short for "F1 Racing" - named after the standard "help" key in Windows, it's a sport where participants desperately search through software help files trying to find actual documentation. It's tedious and somewhat cruel, most matches ending in a draw as no participant is able to find anything helpful. - Shog9

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                  Paul Conrad
                  wrote on last edited by
                  #59

                  Ed.Poore wrote:

                  :nod politely and pretend to understand:

                  :laugh::laugh::laugh: When I look at my old take-home final exam for that Super Visualization course, I still scratch my head over the wavelet transforms stuff :-D

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                  • E Ed Poore

                    Jun Du wrote:

                    This is a perfect example that how people make things more complicated than they should be

                    Maybe it's more complicated but it works. Here's the proof using simple Pythagorean trig and his theorem.

                    Start with a 3,4,5 triangle with height 3 and width 4 (and hypotenuse 5).
                    If A is the bottom left-corner, located over an "origin" of (0,0) then it follows that
                        A = (0,0) (bottom-left corner)
                        B = (4,3) (top-right corner)
                        C = (4,0) (bottom-right corner)
                        θ = Angle BAC (i.e. bottom-left)
                    Also it can be shown (through Pythagorean Trigonometry) that:
                        sin(θ)=3/5
                        cos(θ)=4/5
                        tan(θ)=3/4

                    So you require 20% of the line AB (in this case it is (0.2*5) = 1).
                    We can let the co-ordinates of the end point of this line (from A along AB for 20% of AB) be X=(x,y).
                    It then follows that since we have a hypotenuse equal to 1 and the angle has remained the same that:

                    x = 1*cos(θ) = 4/5
                        y = 1*sin(θ) = 3/5

                    So from A the new point X which is 20% of the line AB is A+X, i.e: X = (0 + 4/5, 0 + 3/5) = (4/5, 3/5).

                    If you take you're equations of:
                        x = a + 0.2 * (c - a)
                        y = b + 0.2 * (d - b)
                    You will get the following answers for this case:
                        x = 0 + 0.2 * (4 - 0) = 0.2 * 2 = 2/5
                        y = 0 + 0.2 * (3 - 0) = 0.2 * 3 = 9/10
                    Which is not the same as the ones above.

                    The simplest proof that the previous equations are wrong can be shown quite simply by Pythagoras' Theorem.
                    If we assume that the triangle formed is of height and width 1 then, your equations show that the height and width of the "new" triangle which provides 20% of AB are both 0.2.
                    If you use Pythagoras on these you get a hypotenuse of √(0.2²+0.2²) which gives √0.08 which is ~0.2828, not 0.2 as you require.


                    Formula 1 - Short for "F1 Racing" - named after the standard "help" key in Windows, it's a sport where participants desperately search through software help files trying to find actual documentation. It's tedious and somewhat cruel, most matches ending in a draw as no participant is able to find anything helpful. - Shog9

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                    Jun Du
                    wrote on last edited by
                    #60

                    Ed.Poore wrote:

                    x = 1*cos(θ) = 4/5 y = 1*sin(θ) = 3/5

                    This is wrong. The length of hypotenuse is 5, not 1.

                    Ed.Poore wrote:

                    x = 0 + 0.2 * (4 - 0) = 0.2 * 2 = 2/5 y = 0 + 0.2 * (3 - 0) = 0.2 * 3 = 9/10

                    This is wrong. How come 4-0 becomes 2, 0.2*3 becomes 9/10? If you hadn't made these mistakes, you could have just proved my formulas, but in a complicated way. - It's easier to make than to correct a mistake.

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                    • P Paul Conrad

                      Ed.Poore wrote:

                      :nod politely and pretend to understand:

                      :laugh::laugh::laugh: When I look at my old take-home final exam for that Super Visualization course, I still scratch my head over the wavelet transforms stuff :-D

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                      Ed Poore
                      wrote on last edited by
                      #61

                      Good, not just me then


                      Formula 1 - Short for "F1 Racing" - named after the standard "help" key in Windows, it's a sport where participants desperately search through software help files trying to find actual documentation. It's tedious and somewhat cruel, most matches ending in a draw as no participant is able to find anything helpful. - Shog9

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