While housing mortgage loan has asset scale and good quality, which suits to be the point of tangency into asset securitization of our country.

The paper takes teaching environment as point of tangency, gives an thorough analysis on the constructing element of teaching environment and educational equipment as well as their mutual relations.

The tangency point of Bottom Hole Assembly is located at where the drill string just touches the wall of the borehole, and the contact force is zero here.