1. Reciprocal is a more complex, too complex if you ask me, for of finding the reverse of an equation, it is done by factorising the coefficients within a formula, then multiplying out and dividing by the common factor in reference to the previouslt identified coefficient series.
2. Handel's left rule states, that light rays coming from the sun, or any other stars, cannot be refracted in certain ways, depending on the speed of rotation, the left hand element is somewhat irrelevant.
3. The reason for this speed being calculated, is due to the derivation of first finding the reciprocal, then substituting values into the equation having made a correlation between the suns ray exposure and its refraction, then you come out with the figure previously quoted.