import proveit
theory = proveit.Theory() # the theorem's theory
from proveit import x, defaults
from proveit.numbers import zero, greater
from proveit.numbers.number_sets.real_numbers import real_pos_def
%proving positive_if_in_real_pos
$\mathbb{R}^{+} = \{r | r > 0\}_{\mathbb{R}}$
defaults.assumptions = positive_if_in_real_pos.conditions
from proveit.numbers.number_sets.real_numbers import real_pos_def
real_pos_def
x_in_real_pos = defaults.assumptions[0]
x_in_real_pos_assumption = x_in_real_pos.prove()
x_in_real_pos_assumption.inner_expr().domain.substitute(real_pos_def)
# %qed