The next step is to actually measure the radius at selected angles of theta. In this example we have provided the protractor, so you only need a ruler.

Plotting the increase of radius with increasing theta will produce a curved graph. To change this into a linear graph we need to use the logarithmic function:

y = a^x expressed as

log y = x*log a. The logarithmic spiral,

r =k^theta becomes
log r = theta*log k.

Putting this into the form for a linear graph, 
y = m*x + b, 
we have y = log r, x = theta, m = log k, and b = 0. 

So all we have to do is measure the slope m of a plot of theta versus log r. Since 
m = log k, then k = 10^m. 

If you plot a logarithmic spiral using this value for k, it should closely match the curvature of the cornrow braid.