yego.me
💡 Stop wasting time. Read Youtube instead of watch. Download Chrome Extension

Shape properties after a sequence of transformations


3m read
·Nov 11, 2024

In past videos, we've thought about whether segment lengths or angle measures are preserved with a transformation. What we're now going to think about is what is preserved with a sequence of transformations, and in particular, we're going to think about angle measure, angle measure, and segment lengths.

So if you're transforming some type of a shape, segment segment lengths. So let's look at this first example. They say a sequence of transformations is described below. So we first do a translation, then we do a reflection over a horizontal line pq, then we do a vertical stretch about pq.

What is this going to do? Is this going to preserve angle measures, and is this going to preserve segment lengths? Well, a translation is a rigid transformation, and so that will preserve both angle measures and segment lengths. So after that, angle measures and segment lengths are still going to be the same.

A reflection over a horizontal line pq, well, a reflection is also a rigid transformation, and so we will continue to preserve angle measure and segment lengths. Then they say a vertical stretch about pq. Well, let's just think about what a vertical stretch does.

So if I have some triangle right over here, if I have some triangle that looks like this, it says triangle ABC. And if you were to do a vertical stretch, what's going to happen? Well, let's just imagine that we take these sides and we stretch them out so that we now have a is over here or a prime I should say is over there. Let's say that b prime is now over here. This isn't going to be exact.

Well, what just happened to my triangle? Well, the measure of angle C is for sure going to be different now, and my segment lengths are for sure going to be different now. a prime c prime is going to be different than ac in terms of segment length. So a vertical stretch, if we're talking about a stretch in general, this is going to preserve neither. So neither preserved, neither preserved.

So in general, if you're doing rigid transformation after rigid transformation, you're going to preserve both angles and segment lengths. But if you throw a stretch in there, then all bets are off; you're not going to preserve either of them.

Let's do another example. A sequence of transformations is described below, and so they give three transformations. So pause this video and think about whether angle measures, segment lengths, or well, either both, or neither, or only one of them be preserved.

All right, so first we have a rotation about a point P. That's a rigid transformation; it would preserve both segment lengths and angle measures. Then you have a translation, which is also a rigid transformation, and so that would preserve both again. Then we have a rotation about point P, so once again another rigid transformation. So in this situation, everything is going to be preserved.

So both angle measure, angle measure, and segment length are going to be preserved in this example. Let's do one more example. So here once again we have a sequence of transformations, so pause this video again and see if you can figure out whether angle measures, segment lengths, both, or neither are going to be preserved.

So the first transformation is a dilation. So dilation is a non-rigid transformation, so segment lengths not preserved; segment lengths not preserved. And we've seen this in multiple videos already, but in a dilation, angles are preserved; angles preserved. So already we've lost our segment lengths, but we still got our angles.

Then we have a rotation about another point Q, so this is a rigid transformation; it would preserve both. But we've already lost our segment lengths, but angles are going to continue to be preserved. And then finally, a reflection, which is still a rigid transformation, and it would preserve both.

But once again, our segment lengths got lost through the dilation, but we will continue to preserve the angles. So in this series of, after these three transformations, the only thing that's going to be preserved are going to be your angles.

More Articles

View All
Points inside/outside/on a circle | Mathematics I | High School Math | Khan Academy
A circle is centered at the point C which has the coordinates -1, -3 and has a radius of six. Where does the point P, which has the coordinates -6, -6, lie? We have three options: inside the circle, on the circle, or outside the circle. The key realizati…
The Deep Meaning Of Yin & Yang
All information whatsoever can be translated into terms of yang and yin. Alan Watts. The concept of Yin & Yang lies at the basis of Taoist philosophy. It makes a lot of appearances in popular and consumer culture, representing things like balance and…
Limits of composite functions | Limits and continuity | AP Calculus AB | Khan Academy
Let’s now take some limits involving composite functions. So over here we have the limit of G of H of x as x approaches three. And like always, I encourage you to pause the video and see if you can figure this out on your own. Well, we can leverage our l…
_-substitution: defining _ | AP Calculus AB | Khan Academy
What we’re going to do in this video is give ourselves some practice in the first step of u substitution, which is often the most difficult for those who are first learning it. That’s recognizing when u substitution is appropriate and then defining an app…
Khan Academy Ed Talks featuring Brooke Mabry - Wednesday, December 16
Hi everyone, Sal Khan here from Khan Academy. Welcome to our Ed Talks Live, this new flavor of homeroom that we’re doing. We have a very exciting conversation with Brooke Mabry about learning loss, summer slide, and actually our partnership with NWEA as w…
Compare with multiplication examples
This here is a screenshot from this exercise on Khan Academy. It says the number 48 is six times as many as eight. Write this comparison as a multiplication equation. So pause this video and see if you can have a go at that. All right, so it sounds very …