Unit 1: Section 1: I can apply the segment addition postulate and the angle addition postulate

Unit 1

Section 1: I can apply the Segment Addition Postulate and the Angle Addition Postulate

Welcome, once again, to the class blog! Today, we will be piecing together two very important postulates that will be used almost constantly in the future. I feel like it should be said that you should not read further in this section until you have read and quizzed the vocabulary post. 

Without further ado, here are the two addition postulates.

Segment Addition Postulate

If a point B lies on a line segment AC, then

AB + BC = AC.

Visually, here's what this looks like.

Figure 1: Line segment AC, with point B

I know it might seem like a lot to take in, but the jist of it is this: "the red part plus the blue part equals the whole thing." I also like to sum it up thusly:

PART + PART = WHOLE

Catching The Bus

A great example of this is if you have ever walked from your home to a bus stop to catch a bus. In your brain, all of you do a little bit of math while you're walking (or skating or biking) to your stop. You figure: if it is A blocks from home to the street and then B blocks down the street to the stop, then it must be C blocks from home to the stop.

In this situation, it would be quite easy to use the segment addition postulate to find the total distance to the bus stop. All you have to do to find the whole is add the parts.

That is a simple example. To see a more complex example, check out the video below.

Some of you may feel like this example is "way too complicated," or you might be tempted to tell me that this is "just too much, Mr. Shock." And I, of course, would remind you 1) you are all capable of algebra, 2) this is school, after all, and 3) my job is to help you learn new things, so stick with it!

Angle Addition Postulate

If a point B lies on the interior of angle AOC, then

Visually, here's what it looks like:

Figure 2: Angle AOC with interior point B

I know it might seem like a lot to take in, but the jist of it is this: "the red part plus the blue part equals the whole thing." I also like to sum it up thusly:

PART + PART = WHOLE

Summary

It is at this point that I will provide a wrap-up for what you have read. And today, the take-away really is quite simple: in geometry, part plus part equals whole. That's it!

"But, Mr. Shock," you're thinking (or saying aloud to your phone screen or computer for some odd reason), "surely it can't be that simple! Our first lesson in Geometry class can't just be that two (or more) parts add up to the whole! That's too easy!"

And you would be wrong. That is the entirety of the lesson today. Your first lesson of Geometry class really is that two - or more - parts make up a whole. And don't call me Shirley.

Figure 3: A scene from Airplane!

Attached Work

Now that you've read today's lesson, don't forget to practice your Segment Addition Postulate and your Angle Addition Postulate, Also, don't forget to take the Online Quiz for this section.