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### Course: High school geometry>Unit 2

Lesson 3: Properties & definitions of transformations

# Identifying type of transformation

Sal is given information about a transformation in terms of a few pairs of points and their corresponding images, and he determines what kind of transformation it can be. Created by Sal Khan.

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• I've never been more frustrated in my life, I do not get frustrated easily, as a matter of fact I've never been frustrated, this is the first time I feel angry at math exercises, the quantitatively defining regid transformations is really bad, there is no explanation as to how you can find out where the center of rotation is, there must be a tool that helps you find where you can place the center to do a rotation affecting multiple points.
• Miguel-
If you should still be on KA, please know that this particular aspect of Geometry can be tricky to get your head around. I was half-way thru the calculus playlist and exercises and when these Transformations videos and exercises turned up and I found them challenging, to say the least. Others have made this recommendation: start at the top of the playlist and go thru it systematically. Do all the exercises, multiple times if needed, and look at the hints, even if you got something correct. Use graph paper and pencil; get a tactile sense of what is going on. I found some of these exercises cumbersome on the computer screen, but they really pop-out when transferred to paper. If you really feel like you've done everything to understand a problem or concept and you feel that the site is not giving you the right info or confusing info, let KA know. They may take a while to respond but I know that they want to be informed of what is working or not working.
• This video makes sense, I get all parts shown is this video and the past two on the subject. However they are nothing like the questions I have been getting in Precisely defining rigid transformations exercise. Also some of those questions don't even have points to the point where i'm not able to figure it out. (I'm talking about the questions formatted with the bubbles, no graphs what so ever). So what do I do about this exercise when I can't even do it.
• Open all of the hints and read them and take notes, then use that information when you go through more questions.
• what does it mean by
Preserves angle measures and segment lengths
Preserves all angle measures only
Preserves all segment lengths only?
• Preserves angle measures and segment lengths: means that after whatever transformation you perform, the angles are the same and the lengths of the sides are also unchanged. For instance, if you have a triangle and you translate it by (-7, 3) it is still exactly the same size with the same angles. Ditto for rotations.
Preserves all angle measures only: means that the lengths may change, but the angles remain the same. For instance, in a dilation, the figure gets bigger or smaller, but the angles don't change.
(BTW, for those that have done the congruent/similar playlists, the first is describing a figure that is congruent to the original figure after transformation and the second is describing a figure that is no longer congruent but is still similar to the original figure.)
Preserves all segment lengths only: The angles change but the sides remain the same length. Does anyone have an example for this one?
• The problem with this video is that it has nothing to do with Precisely Defining Rigid Transformations, which is about whether doing an operation to the coordinates of an object with preserve its angle measures, side lengths, both, or neither. Why is this labeled as "Stuck? Watch a video." when it doesn't help with the subject?
• Out of curiosity, I wonder where the exercises for this lesson have gone. (At least, I don't see them in this section.) Anyone know?
• I think it's just an extra video to help you understand more.
• For the problem at : would a rotation around a point like (-6, -6) be a solution? Or any point that all 4 points are equidistant from? (I've just eyeballed point (-6, -6).)
• Not necessarily. You have to remember that you would be rotating along a non-linear line, so it would be somewhat off.
Hope this helps!
(1 vote)
• An associated Exercise says there exists a Map which takes A to A' and B to B'. It also asserts that the quadrilateral AA'BB' is a parallelogram. The hints say thats proof the Map is a translation.

But what if the translation for A to A' is parallel but opposite in direction to the translation of B to B'?
Usually in these exercises, we get it wrong if we assume something not given. (E.g., in rotation questions when they say the angle after rotation is the same but they omit that distance is unchanged, the answer is that's not enough info to call it a rotation.)

• It wouldn't be a parallelogram if you translated A in one direction and B in the opposite direction. The line A' to B' would cross the line from A to B, forming two triangles rather than a parallelogram. It helps me to sketch out the situation.
(1 vote)
• In , why can't it be a translation? I didn't understand.