Differential Equations diameter of a spiral

1. Jan 2, 2005

Goo_Gal1

how can I calculate the "diameter" of a spiral ? someone told me i need to use Differential or Integral Equations to solve this, but i'm not sure how.

If there is a spiral that it's radius increases by 1 cm for every radian until the radius reaches the size R . how can I calculate the length of the line that the spiral consists of?

2. Jan 2, 2005

mathwonk

try parametrizing it by angle.

3. Jan 2, 2005

dextercioby

That's the Spiral of Archimedes.For details check this wonderful site (warning:it's in French):
spiral of Archimedes

Daniel.