Measure angle at intersection between co-planar circle and Fibonacci spiral

Hi, I want to measure the angle in the x-y plane between the tangents of a co-planar Fibonacci spiral at intersection of a 9" dia. circle. What is the best way to do this?
Please see the attached.
Thanks. ~ David
Generated by fibonacciSpiral_TDW_040415.ghx_on_041615_55CW_34CCW.3dm (228.3 KB)

Admin, please delete this post.

why not describe your solution?

For tangent to Spiral select Curve>Line>Tangent from Curve, use Int snap for start of tangent to spiral at intersection with the 9" circle, then Point for end of line a convenient distance and direction away from the intersection. Repeat the process for tangent to the circle.
Then select Analyze>Angle