OCT.18th.2014 CSC165 Proof

In this week lecture,we learned how to make a proof.

Some points should be made attention:
1) the form and the structure of a proof
2)the key point(maybe the most complicate part)
3)the  annotation

sometimes we find the statement to difficult to proof, we could think about the contrapositive or the negation of the origin, since they have connections to it.


proof by cases
In such problems, the provident should be separated into several cases.such that case, case2 and so on (i.e to prove all natural number, we should divide them into case1: odd number case2: even number)

when we need to prove a existence we just need only one element.