Proof of proveit.numbers.functions.one_over_x_sqrd_in_mon_dec_fxns theorem

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

%proving one_over_x_sqrd_in_mon_dec_fxns

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