 Hello, geometricians and logicians. Today is your introduction to flow proofs. The reason we work with proofs is because in geometry that is a way to be absolutely certain that you can say something is true using deductive reasoning, which you've learned about during this section on logic. There is no note sheet for this section, so get out your notebook and we need you to copy these notes about the five essential parts to a good proof. Pause the video and copy down these five points of important parts to a good proof. Now that you have those copied down, I need you to be aware or remember, these are things you learned back in middle school, but remember some of the properties of algebra. You don't need to copy these down. These are on page 111 in your textbook, but these properties are the things we're going to use when we design our proof. A proof will have a statement, a mathematical statement, and then a reason for each statement. And these properties are the reasons why we can say something or move from one step to the next step in a proof. So it's important for you to kind of remember these properties and have them in mind. Again, if you choose to copy them down, that's great. If you don't want to copy them down, you don't have to. We will be using them in the subsequent proofs.