Help with trigonometrics

[czardas]

Probably doesn't help much, but here goes anyway. As the thickness of the wire decreases, the closer the cross section area of wire required (wire thickness * wire length) approaches the surface area of the sphere (green line in the 1st post). This is an asymptotic relationship.

So you can work out a pretty close approximation of the length of wire needed with either thin wire, or large spheres. You can also work out the angle of change if concentric circles are used (not joined as jchd put it), by turning the circumference (green line in the 1st post) into something close to an equilateral polygon (red line below). There will normally be a small incomensurable amount left over - negligable witth thin wire and large spheres.

This is similar to the method for calculating pi.

The arc distance where the red line meets the outer circumference represents the thickness of the wire (in this cross section approximation of your spherical coil). I find visual representations like this often make a problem easier to conceptualize. I hope that made some sense.

The polygon needs a few more sides though!

Edited November 26, 2013 by czardas

[jchd]

 

But when I try to do the loop with C = (R-r)sin(A)  I fail somewhere

Read again the help file under Sin() and provide the function with an angle value in radians, not degrees. 360° = 2 Pi

[Qwerty212]

Read again the help file under Sin() and provide the function with an angle value in radians, not degrees. 360° = 2 Pi

 

You are completely right. I though that the function sin() was called using degrees.

Thanks a lot for your help (and to the other who have taked the time to read).

Greets from Barcelona