French philosopher Montesquieu wrote a book about "tripartite systems" (3 systems), Government. This system separate how are two different bodies. How does his ideas apply to the US Constitution?

The theory of Montesquieu, which defends the separation of powers was implemented in many constitutions around the world. It was implemented in the US Constitution, because the founding fathers considered that the American states sufferd abuse from the powers of the monarchy and parlamentarism. The constitution limits the powers of the federal government and balances the powers, which are:

Legislative - makes law

Executive - executes and forces the law

Judiciary - interprets and applies the law in the name of the state.