This answer may have been already provided in different wording but I'll thow mine in for good measure.

Converting degrees to inches
The sine of an angle is the hypotenuse (the width of the control surface) divided by the movement.

Example:
Control surface is 2” wide and the movement is 10º

On the calculator, enter 10 press the sin button, then times 2 and = (equal) to get inches in decimal. 10 sin X 2 =.347”


Converting inches to degrees
Inches in decimal, divided by the width of the control surface, = the Inv-Sin

Example:
Movement is .347” and the width of the control surface is 2”

On the calculator, enter .347 divide by 2 then = (equal), then press sin-1 to get the degrees. .347 / 2 = sin-1 = 9.99º

Edit: had titles mixed up :-)