In previous posts we defined porpositions, theorems, corollaries, among others. To demonstrate theorems, it means that the given proposition is a tautology, in which we obtain through the truth tables. Below, we present some methods for demonstrating results. Deductive method The deductive method is obtained through the use of definitions and other pre-established results. For this, we use the implications $(\Rightarrow)$ and logical bi-implications $(\Leftrightarrow)$. Example 1: With the following statements, we will show whether it is a theorem or not. For this, the following hypotheses are: $H_1$: time is money. $H_2$: bum has a lot of time. And the thesis: $T$: Tramp has a lot of money. Is the proposition $H_1 \wedge H_2 \Rightarrow T$ a theorem?