Proof of proveit.linear_algebra.inner_products.spectral_decomposition_as_ortho_ortho_projectors theorem

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

%proving spectral_decomposition_as_ortho_ortho_projectors

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