Rotation is an example of a transformation. The coordinate plane has two axes: the horizontal and vertical axes. ROTATION A rotation is a transformation that turns a figure about (around) a point or a line. A transformation is a way of changing the size or position of a shape. The point a figure turns around is called the center of rotation. Basically, rotation means to spin a shape. The center of rotation can be on or outside the shape. Create a transformation rule for reflection over the x axis. The general rule for rotation of an object 90 degrees is (x, y) -> (-y, x). Delta specifies the distance of the new outline from the original outline, and therefore reproduces angled corners. The most common rotations are 180 or 90 turns, and occasionally, 270 turns, about the origin, and affect each point of a figure as follows: Rotations About The Origin 90 Degree Rotation When rotating a point 90 degrees counterclockwise about the origin our point A (x,y) becomes A' (-y,x). When negative, the polygon is offset inward. In other words, switch x and y and make y negative. No inward perimeter is generated in places where the perimeter would cross itself.

And so this would be negative 90 degrees, definitely feel good about that.(default false) When using the delta parameter, this flag defines if edges should be chamfered (cut off with a straight line) or not (extended to their intersection). And this looks like a right angle, definitely more like a rightĪngle than a 60-degree angle. And once again, we are moving clockwise, so it's a negative rotation. This is where D is, and this is where D-prime is. Point and feel good that that also meets that negative 90 degrees. This looks like a right angle, so I feel good about We are going clockwise, so it's going to be a negative rotation. Too close to, I'll use black, so we're going from B toī-prime right over here. Let me do a new color here, just 'cause this color is Much did I have to rotate it? I could do B to B-prime, although this might beĪ little bit too close. I can take some initial pointĪnd then look at its image and think about, well, how I don't have a coordinate plane here, but it's the same notion. Well, I'm gonna tackle this the same way. So once again, pause this video, and see if you can figure it out. So we are told quadrilateral A-prime, B-prime, C-prime,ĭ-prime, in red here, is the image of quadrilateralĪBCD, in blue here, under rotation about point Q. So just looking at A toĪ-prime makes me feel good that this was a 60-degree rotation. And if you do that with any of the points, you would see a similar thing. Another way to thinkĪbout is that 60 degrees is 1/3 of 180 degrees, which this also looks Like 2/3 of a right angle, so I'll go with 60 degrees. One, 60 degrees wouldīe 2/3 of a right angle, while 30 degrees wouldīe 1/3 of a right angle. This 30 degrees or 60 degrees? And there's a bunch of ways The counterclockwise direction, so it's going to have a positive angle. And where does it get rotated to? Well, it gets rotated to right over here. Remember we're rotating about the origin.

Points have to be rotated to go from A to A-prime, or B to B-prime, or from C to C-prime? So let's just start with A. So I'm just gonna think about how did each of these So like always, pause this video, see if you can figure it out. We're told that triangle A-prime, B-prime, C-prime, so that's this red triangle over here, is the image of triangle ABC, so that's this blue triangle here, under rotation about the origin, so we're rotating about the origin here.

90 degrees rotations rules geometry