#Geometry rules of rotation how to
#Geometry rules of rotation full

That this is equivalent to a positive 90 degree rotation. Get that point here, which we could have also gotten there by just rotating it by And then this would beĪnother negative 90, which would give you in total, negative 270 degrees. This would be rotatingĪnother negative 90, which would, together, be negative 180. The origin by negative, so this is the origin here, by negative 270 degrees, what would that be? Well let's see, this wouldīe rotating negative 90. If you were to start right over here and you were to rotate around So if I were to start, if I were to, let me draw some coordinate axes here. So let's just first thinkĪbout what a negative 270 degree rotation actually is. So actually let me go over here so I can actually draw on it. The points of this triangle around the origin by negative 270 degrees, where is it gonna put these points? And to help us think about that, I have copied and pasted So what we want to do is think about, well look, if we rotate And this tool, I can put points in, or I could delete points. So positive is counter-clockwise, which is a standard convention, and this is negative, so a negative degree would be clockwise. The direction of rotationīy a positive angle is counter-clockwise. So this is the triangle PINĪnd we're gonna rotate it negative 270 degrees about the origin. We're told that triangle PIN is rotated negative 270ĭegrees about the origin. I hope this gives you more of an intuitive sense. If you want, you can connect each vertex and rotated vertex to the origin to see if the angle is indeed 90 degrees. As per the definition of rotation, the angles APA', BPB', and CPC', or the angle from a vertex to the point of rotation (where your finger is) to the transformed vertex, should be equal to 90 degrees. The rotated triangle will be called triangle A'B'C'. The point at which we do the rotation, we'll call point P. Well, let's say the shape is a triangle with vertices A, B, and C, and we want to rotate it 90 degrees. The shape is being rotated! But how do we do this for a specific angle? With your finger firmly on that point, rotate the paper on top. Now place your finger on the rotation point. Put another paper on top of it (I like to imagine this one as being something like a transparent sheet protector, and I draw on it using a dry-erase marker) and trace the point/shape. Here's something that helps me visualize it: The 'formula' for a rotation depends on the direction of the rotation. I'm sorry about the confusion with my original message above. If you want to do a clockwise rotation follow these formulas: 90 = (b, -a) 180 = (-a, -b) 270 = (-b, a) 360 = (a, b). Also this is for a counterclockwise rotation.

#Geometry rules of rotation full

360 degrees doesn't change since it is a full rotation or a full circle. 180 degrees and 360 degrees are also opposites of each other. So, (-b, a) is for 90 degrees and (b, -a) is for 270.

When plot these points on the graph paper, we will get the figure of the image (rotated figure).The way that I remember it is that 90 degrees and 270 degrees are basically the opposite of each other. In the above problem, vertices of the image areħ. When we apply the formula, we will get the following vertices of the image (rotated figure).Ħ. When we rotate the given figure about 90° clock wise, we have to apply the formulaĥ. When we plot these points on a graph paper, we will get the figure of the pre-image (original figure).Ĥ. In the above problem, the vertices of the pre-image areģ. First we have to plot the vertices of the pre-image.Ģ.

#Geometry rules of rotation how to

So the rule that we have to apply here is (x, y) -> (y, -x).īased on the rule given in step 1, we have to find the vertices of the reflected triangle A'B'C'.Ī'(1, 2), B(4, -2) and C'(2, -4) How to sketch the rotated figure?ġ. Here triangle is rotated about 90 ° clock wise.

If this triangle is rotated about 90 ° clockwise, what will be the new vertices A', B' and C'?įirst we have to know the correct rule that we have to apply in this problem. Let A(-2, 1), B (2, 4) and C (4, 2) be the three vertices of a triangle. Let us consider the following example to have better understanding of reflection. Here the rule we have applied is (x, y) -> (y, -x). Once students understand the rules which they have to apply for rotation transformation, they can easily make rotation transformation of a figure.įor example, if we are going to make rotation transformation of the point (5, 3) about 90 ° (clock wise rotation), after transformation, the point would be (3, -5).