Equation for a spiral, confused?!?

[noppenbd]

The values for all trig functions are in degrees.



For this reason, if you want a spiral which reaches radius 5 at one revolution (t=1), you should use:



r= 5 * sin (90*t) + .095



theta = 360 * t



z=0



Hope this helps.

 

[noppenbd]

Just to be anal ...



It does make a difference what you choose as the operand for the sin function. See the following image:



View attachment 272



The inner curve is using your original equations, the outer one uses



r = .087262*sin(90*t)+.095



theta = 360*t



z= 0



As you can see, both have the same starting and ending radii, the difference is that the outer curve ends with tangency parallel to the rotation direction. Not sure if it matters, but I had fun playing with the curves anyway!