[PD] Equal panning formulas

[jlistshit]

Please excuse this question not entirely being related to Pure Data.

If i feed values 0-1 from linear [hsl] into either

[expr sqrt(1-$f1); sqrt($f1)]

or

[expr cos(1.57 * $f1); sin(1.57 * $f1)]

i essentially get the same set of output values, but with different input values. Obviously 0.5 puts both formulas to output 0.707 on both sides, but only extremes or center position input values (0, 1, 0.5) output the same results. 
The square root function leads to locations more near to the center, the other one has a wider image. 

A. Which one is the correct one from an engineering view point, and where are special cases which might lead to using the other one instead?

One of those cases occurs to me, when i have a foreground signal with a wide stereo image, but want a stereo reverb generated from this to be yet stereo, but responding stronger in the center.

B. What if i want to favor the center even more, though without leaving the idea of equal power panning (ah ja, mix it with a mono signal…, but which of the two formulas will i have to use then???)

Thank you very much in advance.

jayrope
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