Notices
Results 1 to 5 of 5

Thread: need eguation

  1. #1 need eguation 
    Forum Freshman
    Join Date
    Apr 2006
    Location
    the sticks
    Posts
    24
    i am writing a program that draws the arcs produced by rotating one coin around another.

    given the diameters of the coins can someone provide the sine/cosine functions in polar coordinates i would need?


    Reply With Quote  
     

  2.  
     

  3. #2  
    Forum Freshman omerta's Avatar
    Join Date
    Aug 2006
    Location
    Cincinnati, OH
    Posts
    40
    I could be wrong and someone correct me if I am but maybe you should check parametric equations. Where the curves of x/y can vary around or by a parameter. One example shows a circle inside a larger circle and the path that a point on the small circle traces out as it rotates inside of the larger circle. I dont see an equation but it is called a Hypocycloid of four cusps.

    http://en.wikipedia.org/wiki/Hypocycloid

    ^Has some good info and should help but honestly I dont know enough about the equations to know if they hold for a circle transversing around the outside. Thats pretty neat stuff though, good luck.


    I've always wanted to know why. Just takes me a little longer than most, lol.
    Reply With Quote  
     

  4. #3  
    Forum Freshman omerta's Avatar
    Join Date
    Aug 2006
    Location
    Cincinnati, OH
    Posts
    40
    This is probably what you want for a coin rolling on the outside of another.

    http://en.wikipedia.org/wiki/Epitrochoid

    Wow I remember all those shapes from growing up and owning a spirograph, lol. Those were fun.
    I've always wanted to know why. Just takes me a little longer than most, lol.
    Reply With Quote  
     

  5. #4  
    Guest
    Without giving you all the answers to your homework think about it,

    x=x_axis_origin
    y=y_axis_origin

    for t = 0 to 360$
    x1=x+ sin(t)*large_coin_radius
    y1=y+ cos(t)*large_coin_radius
    x2=x1+ sin(t*ratio_of_radius)*small_coin_radius + small_coin_radius
    y2=y1+ cos(t*ratio_of_radius)*small_coin_radius + small)_coin_radius
    plot X1,Y1. or line -(x1,y1)
    Next t


    $ assumes degrees but it's usually in radians ie pi/180 rathre than 360.

    I know it can be more elegant but the code above should be easier to read.

    Here's a working VB example:

    You'll need to tweak the values as required...

    Private Sub Command1_Click()
    x = 3700
    y = 3700

    For t = 0 To 180 / 3.14159 Step 0.001
    X1 = x + Sin(t) * 2400
    Y1 = y + Cos(t) * 2400
    X2 = X1 + Sin(t * 8 ) * 200 '
    Y2 = Y1 + Cos(t * 8 ) * 200
    If t = 0 Then Picture1.PSet (X2, Y2)
    Picture1.Line -(X2, Y2)
    Next t
    End Sub
    Reply With Quote  
     

  6. #5  
    Forum Freshman
    Join Date
    Apr 2006
    Location
    the sticks
    Posts
    24
    thanks guys. the equation for the epicycloid is what i needed.
    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •