Answer: definitions, hypothesis, previously proved theorems
Explanation:
Deductive reasoning can be defined as the process of reasoning in which two or more statements are used to reach a logically valid conclusion. The deductive reasoning always leads in the direction of condition, links, premises and finally reaches up to a conclusion.
Definition, hypothesis and previously proved theorems can lead to forming a valid conclusion. Hence, these help in deductive reasoning.
A definition can be defined as a statement which includes a meaning of a term.
A hypothesis can be defined as the proposed explanation for the phenomena based on observations and facts.
Previously proved theorems are based upon proves developed by application of scientific methodology.