In construction.
Manners are at the basis of all education and University is about High Education
Forbidden expressions when talking to your colleagues: " this is trivial", "this is obvious". [Implied message: "if you do not understand, you are stupid"]
Instead, be precise, use, as applicable, "it follows from the definition", "it is a straightforward computation", "if follows from property X", "we have found a tautology",....