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The polytropic index (n) is given by
log (p1p2)/log (v1v2)
log (p2/ p1)/log (v1/ v2)
log (v1/ v2)/ log (p1/p2)
log [(p1v1)/(p2v2)]
log (p1p2)/log (v1v2)
log (p2/ p1)/log (v1/ v2)
log (v1/ v2)/ log (p1/p2)
log [(p1v1)/(p2v2)]