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 June 13th, 2018, 04:42 AM #1 Newbie   Joined: Jun 2018 From: Groningen Posts: 14 Thanks: 0 How can I make lines of equal lengths to all directions from a central point? I made a problem in my mind that I can't seem to solve. I need an answer because it is quite fundamental to me, because it is about the expansion of things like the universe. This is the problem; I can't understand how to make lines of equal lengths to all directions from a central point. I wrote a blogpost on my website to explain the thoughts and methods I have tried. Could someone please help me? How can I make lines of equal lengths to all directions from a central point? – JUSTIN TIMMER
 June 14th, 2018, 03:13 AM #2 Global Moderator   Joined: Dec 2006 Posts: 19,988 Thanks: 1855 Start my making one line of the required length, then fix one end of it and allow the other end to move freely while the (moving) line is kept straight.
 June 14th, 2018, 01:49 PM #3 Global Moderator   Joined: May 2007 Posts: 6,642 Thanks: 627 In two dimensions draw a circle and three dimensions a sphere, centered at the point in question. In both cases radii are the lines you want. This sounds too simple, so what am I missing?
June 14th, 2018, 04:41 PM   #4
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 Originally Posted by justintimmer How can I make lines of equal lengths to all directions from a central point? ï¿½ JUSTIN TIMMER
Oh I see. You want to study computer graphics. How you make smooth-looking circles, how you determine if a point is inside or outside of a region, etc. You're looking for an algorithm for drawing a circle or a sphere. Computer graphics has solved all these problems.

June 14th, 2018, 07:25 PM   #5
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 Originally Posted by justintimmer I made a problem in my mind that I can't seem to solve. I need an answer because it is quite fundamental to me, because it is about the expansion of things like the universe. This is the problem; I can't understand how to make lines of equal lengths to all directions from a central point. I wrote a blogpost on my website to explain the thoughts and methods I have tried. Could someone please help me? How can I make lines of equal lengths to all directions from a central point? ï¿½ JUSTIN TIMMER
I have no idea what that linked site is supposed to mean. But you seem to be asking a question in basic trigonometry.

In two dimensions, using a reference angle $\theta$ relative to the x-axis in degrees and a length a from the origin when $\theta = 0$:

$\sin( \theta ) = \dfrac{y}{a} \implies y = a * \sin ( \theta ); \text { and}$

$\cos ( \theta ) = \dfrac{x}{a} \implies x = a * \cos ( \theta ).$

That gives you the x and y co-ordinates of the end points of lines drawn from the origin with length a at various angles to the x-axis. Be sure to use sine and cosine functions in degrees. I do not want to explain radians.

Last edited by skipjack; June 15th, 2018 at 07:10 AM.

 June 21st, 2018, 09:04 AM #6 Newbie   Joined: Jun 2018 From: Groningen Posts: 14 Thanks: 0 Further explanation of my problem Hi, sorry for not being clear in the blogpost/introduction of the thread. But very much thanks for your responses either way! I hope I can make it a little more clear this way: Basically, I want to find out how you make a structure that expands evenly to all directions (like with the big bang). How did the universe expand from one point to a "spherical" filled structure? Example, suppose you stand at the origin of the axes (x,y,z) with a hosepipe turned on. How do you fill the area around you to the shape of a sphere? Fixing one end and move the other end wouldn't be allowed because that is only expansion towards one side. Drawing a circle and finding the center is also not allowed because, then you don't start at the center. But how do you do that?
June 21st, 2018, 09:57 AM   #7
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 Originally Posted by justintimmer Fixing one end and move the other end wouldn't be allowed because that is only expansion towards one side. Drawing a circle and finding the center is also not allowed because, then you don't start at the center.
This is an interesting question. Perhaps some kind of space-filling curve applied to a circle. It seems reasonable that there's a sphere-filling curve.

 August 9th, 2018, 01:35 AM #8 Newbie   Joined: Jun 2018 From: Groningen Posts: 14 Thanks: 0 Thanks for appreciating the question. With a space-filling curve, would you mean a fractal like curve?

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