import proveit
theory = proveit.Theory() # the theorem's theory
from proveit import defaults
from proveit import x, alpha
from proveit.linear_algebra import ScalarMult
%proving scalar_mult_eq
defaults.assumptions = scalar_mult_eq.all_conditions()
x_eq_y = defaults.assumptions[-1]
x_eq_y.substitution(ScalarMult(alpha, x))
%qed