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Math Problem ...

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  • R Red Stateler

    You should change your name to OneFifthMan.

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    HalfWayMan
    wrote on last edited by
    #4

    Urm... I don't get it :((

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    • H HalfWayMan

      Urm... I don't get it :((

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      Red Stateler
      wrote on last edited by
      #5

      0.5 = 1/2. 0.2 = 1/5. Get it???? :laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh: :laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh: :laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh: :laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh: :laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh: :^)

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      • R Red Stateler

        0.5 = 1/2. 0.2 = 1/5. Get it???? :laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh: :laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh: :laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh: :laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh: :laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh: :^)

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        HalfWayMan
        wrote on last edited by
        #6

        But 20% = 0.2. I hope. :^) -- modified at 13:03 Tuesday 13th June, 2006 ;)

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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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          Eric Dahlvang
          wrote on last edited by
          #7

          I'm no math whiz, but can't you just: .2(a+c)=e .2(b+d)=f ef=20% between ab & cd That was stupid. I thought about it, and I think this would work: a+(.2(c-a))=e b+(.2(d-b))=f ef=20% between ab & cd If that isn't right, then I'm too dumn to figure it out without more coffee. ---------- Some problems are so complex that you have to be highly intelligent and well informed just to be undecided about them. - Laurence J. Peters -- modified at 13:11 Tuesday 13th June, 2006

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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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            Rohde
            wrote on last edited by
            #8

            1. Translate the point to the origin (remember the translation) 2. Get the position vector of the second point 3. Calculate the length of the vector 3. Normalize the vector 4. Multiply each component with 0.2 x the length from #3 5. Use the inverse translation -- modified at 13:06 Tuesday 13th June, 2006 Oh, I was too late

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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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              J Offline
              Jun Du
              wrote on last edited by
              #9

              Ray Kinsella wrote:

              the point 20% of distance between these two points on the same slope

              If you mean 20% of the distance from the point (a, b), then (e, f)=(a+0.2*(c-a), b+0.2*(d-b)) Otherwise (e, f)=(a+0.8*(c-a), b+0.8*(d-b)) - It's easier to make than to correct a mistake.

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              • H HalfWayMan

                Make a vector between the points [c-a,d-b], normalise the vector (divide it by it's magnitude) and then multiply that by 0.2. Then add this onto [a,b] and you should have that. Now watch me get that all wrong and look a fool :)

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                dighn
                wrote on last edited by
                #10

                If I'm reading the question right (ie 20% of the way from AB to CD or vice versa) I don't think the vector should be normalized, so it's just (CD-AB)*0.2+AB

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                • D dighn

                  If I'm reading the question right (ie 20% of the way from AB to CD or vice versa) I don't think the vector should be normalized, so it's just (CD-AB)*0.2+AB

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                  HalfWayMan
                  wrote on last edited by
                  #11

                  Oh spanner! I think you're right. P.S: Please don't tell my boss I got a question like this wrong! :-O

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                  • R Rohde

                    1. Translate the point to the origin (remember the translation) 2. Get the position vector of the second point 3. Calculate the length of the vector 3. Normalize the vector 4. Multiply each component with 0.2 x the length from #3 5. Use the inverse translation -- modified at 13:06 Tuesday 13th June, 2006 Oh, I was too late

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                    Ray Kinsella
                    wrote on last edited by
                    #12

                    don't get it let a,b=2,3 c,d=6,6 2. vector = 4,3 3. magnitude |v| = 5 4. = <4, 3> huh ? Regards Ray "Je Suis Mort De Rire" Blogging @ Keratoconus Watch

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                    • J Jun Du

                      Ray Kinsella wrote:

                      the point 20% of distance between these two points on the same slope

                      If you mean 20% of the distance from the point (a, b), then (e, f)=(a+0.2*(c-a), b+0.2*(d-b)) Otherwise (e, f)=(a+0.8*(c-a), b+0.8*(d-b)) - It's easier to make than to correct a mistake.

                      R Offline
                      R Offline
                      Ray Kinsella
                      wrote on last edited by
                      #13

                      yep ... figured that out a minute ago .... brain hurts ... too long since school ... thanks to all. Regards Ray "Je Suis Mort De Rire" Blogging @ Keratoconus Watch

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                      • R Ray Kinsella

                        don't get it let a,b=2,3 c,d=6,6 2. vector = 4,3 3. magnitude |v| = 5 4. = <4, 3> huh ? Regards Ray "Je Suis Mort De Rire" Blogging @ Keratoconus Watch

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                        Rohde
                        wrote on last edited by
                        #14

                        Magnitude = 5 20% of 5 = 1. So in this case add the normalized vector to get (2.8, 3.6).

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                        • H HalfWayMan

                          But 20% = 0.2. I hope. :^) -- modified at 13:03 Tuesday 13th June, 2006 ;)

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                          Ed Poore
                          wrote on last edited by
                          #15

                          HalfWayMan wrote:

                          20% = 0.2

                          20% = 0.2 = 2/10 = 1/5 ;P


                          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 Rohde

                            Magnitude = 5 20% of 5 = 1. So in this case add the normalized vector to get (2.8, 3.6).

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                            Ray Kinsella
                            wrote on last edited by
                            #16

                            gotcha now ... thanks ... Regards Ray "Je Suis Mort De Rire" Blogging @ Keratoconus Watch

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                            • R Ray Kinsella

                              yep ... figured that out a minute ago .... brain hurts ... too long since school ... thanks to all. Regards Ray "Je Suis Mort De Rire" Blogging @ Keratoconus Watch

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                              Ed Poore
                              wrote on last edited by
                              #17

                              That won't work since you're actually getting the distance that's Sqrt(2(0.2*0.2)) along the line.  Think of it as a right-angled triangle and you're using getting 0.2 along the x and 0.2 along the y so you're actually getting closer to 0.3 along the line. Give me 5 mintues and I'll write out the solution (I hope I'm right :rolleyes:)


                              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

                              Last modified: 13 June 2006 13:25:47 --

                              1 Reply Last reply
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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

                                E Offline
                                E Offline
                                Ed Poore
                                wrote on last edited by
                                #18

                                Ok, a reference image is provided @ http://ed.poore.googlepages.com/question.bmp[^] Basically: Let A=(a,b) Let B=(c,d) Let P=(x,y) (the point where you want to find) |AB| = √((c - a)²+(d - b)²)

                                θ = arctan((d - b) / (c - a))

                                x = a + (0.2*|AB|*cos(θ)) y = b + (0.2*|AB|*sin(θ))

                                Some basic trig and pythagoras, you can do this by vectors, but it essentially boils down to the same thing if I remember correctly (better remember correctly since I might need it for my exam on Friday).


                                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

                                J C P 3 Replies Last reply
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                                • E Ed Poore

                                  Ok, a reference image is provided @ http://ed.poore.googlepages.com/question.bmp[^] Basically: Let A=(a,b) Let B=(c,d) Let P=(x,y) (the point where you want to find) |AB| = √((c - a)²+(d - b)²)

                                  θ = arctan((d - b) / (c - a))

                                  x = a + (0.2*|AB|*cos(θ)) y = b + (0.2*|AB|*sin(θ))

                                  Some basic trig and pythagoras, you can do this by vectors, but it essentially boils down to the same thing if I remember correctly (better remember correctly since I might need it for my exam on Friday).


                                  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

                                  J Offline
                                  J Offline
                                  Jun Du
                                  wrote on last edited by
                                  #19

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

                                  x = a + (0.2*|AB|*cos(θ))) = a + 0.2*(c-a);
                                  y = b + (0.2*|AB|*sin(θ))) = b + 0.2*(d-b);

                                  BTW, I like your "θ". How come It shows "θ" in my editing panel, but not in the post? ...maybe because of my Linux (I'm using RedHat 8 at work). Signature for today: "Don't discuss math problems with a methematician."

                                  P E 3 Replies Last reply
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                                  • E Ed Poore

                                    Ok, a reference image is provided @ http://ed.poore.googlepages.com/question.bmp[^] Basically: Let A=(a,b) Let B=(c,d) Let P=(x,y) (the point where you want to find) |AB| = √((c - a)²+(d - b)²)

                                    θ = arctan((d - b) / (c - a))

                                    x = a + (0.2*|AB|*cos(θ)) y = b + (0.2*|AB|*sin(θ))

                                    Some basic trig and pythagoras, you can do this by vectors, but it essentially boils down to the same thing if I remember correctly (better remember correctly since I might need it for my exam on Friday).


                                    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

                                    C Offline
                                    C Offline
                                    Chris Losinger
                                    wrote on last edited by
                                    #20

                                    just look at that happy happy math! whee! x2 cos(θ4) :) Cleek | Image Toolkits | Thumbnail maker

                                    1 Reply Last reply
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                                    • H HalfWayMan

                                      But 20% = 0.2. I hope. :^) -- modified at 13:03 Tuesday 13th June, 2006 ;)

                                      L Offline
                                      L Offline
                                      led mike
                                      wrote on last edited by
                                      #21

                                      HalfWayMan wrote:

                                      -- modified at 13:03 Tuesday 13th June, 2006

                                      So based on the "date" column showing ( hrs,mins) ago and the "modified" time stamp how long did it take you to get it? :-D

                                      1 Reply Last reply
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                                      • E Ed Poore

                                        Ok, a reference image is provided @ http://ed.poore.googlepages.com/question.bmp[^] Basically: Let A=(a,b) Let B=(c,d) Let P=(x,y) (the point where you want to find) |AB| = √((c - a)²+(d - b)²)

                                        θ = arctan((d - b) / (c - a))

                                        x = a + (0.2*|AB|*cos(θ)) y = b + (0.2*|AB|*sin(θ))

                                        Some basic trig and pythagoras, you can do this by vectors, but it essentially boils down to the same thing if I remember correctly (better remember correctly since I might need it for my exam on Friday).


                                        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

                                        P Offline
                                        P Offline
                                        Paul Conrad
                                        wrote on last edited by
                                        #22

                                        You get a division by zero if you are dealing with vertical lines.

                                        E 1 Reply Last reply
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                                        • J Jun Du

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

                                          x = a + (0.2*|AB|*cos(θ))) = a + 0.2*(c-a);
                                          y = b + (0.2*|AB|*sin(θ))) = b + 0.2*(d-b);

                                          BTW, I like your "θ". How come It shows "θ" in my editing panel, but not in the post? ...maybe because of my Linux (I'm using RedHat 8 at work). Signature for today: "Don't discuss math problems with a methematician."

                                          P Offline
                                          P Offline
                                          Paul Conrad
                                          wrote on last edited by
                                          #23

                                          Though both are correct, I'd go with the simpler way since there is no worries in regards to division by zero. PJC

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