I am trying to find the angle $\theta$ of the following droplet:
I think using $\tan$ is the right way to go, and I thought of using it on the angle formed by the line $r$ and $b$. However, that requires that I can relate it to $\theta$, which isn't clear to me is necessarily the case. I'd be happy to get some help or a push in the right direction.
Hint: The tangent line to a circle is perpendicular to the radius on the intersecting point.