WEEK 6 JOURNAL: PROVE BY CASES

    This week, I learned how to prove a statement by cases. We can divide a statement into several situations, and show that for every situation, this statement is always true. Then, the statement is true. I find using this method can make some problems be easier to solve, because we only need to proof each part of a statement is true, and then the whole statement becomes true. However, the drawback of this method is that when we proof by cases, we must cover all the cases, otherwise the proof won't make sense. For now we have learned several methods to proof a statement is true or false. In some proofs, we need to use several methods to prove, and I think that's the hard point. Because in the sample problems, we only prove each statement by using one single method, and when we need to prove a statement by using several methods, I think it is hard to choose which method I should use and which I should not use.