Two rollers of diameters D1(in mm) and D2 (in mm) are used to measure the internal taper angle in the V-groove of a machined component. The heights H1(in mm) and H2(in mm) are measured by using a height gauge after inserting the rollers into the same V-groove as shown in the figure.
Which one of the following is the correct relationship to evaluate the angle α as shown in the figure?