Proof of proveit.numbers.division.div_real_neg_from_neg_denom theorem

import proveit
theory = proveit.Theory() # the theorem's theory

%proving div_real_neg_from_neg_denom

With these allowed/disallowed theorem/theory presumptions (e.g., to avoid circular dependencies), we begin our proof of
div_real_neg_from_neg_denom:
(see dependencies)