Hi Rom and guest,
I agree this is an interesting question but I would do it differently, Maybe my way is wrong.
Rom I don't think that you found the angle did you?
The staircase goes around the silo much like the label goes around a can of peas
If you take the label off the peas, it is a rectangle.
The length will be the circumference of the can 2*pi*r
and the height will be the hieght of the can.
so
getting back to the silo, the stairs go from the bottom corner of the 'rectangle' to the diagonally opposite corner.
like this.
I wanted to draw the diagram but Geogebra has stopped working for me 


Anyway it is a rectangle. and the stairs are the diagonal.
The rectangle is 37 foot hight and 2*pi*7 = 14pi foot long
The incline angle is the angle between the base and the diagonal.
\(tan\theta = \frac{37}{14\pi}\\ \theta = atan\left( \frac{37}{14\pi} \right)\\ \theta = 40^04'\)
So the angle of incline is 40.072 degrees (3dp)
or 40 degrees and 4 minutes to the nearest minute