![]() In a plane (or, respectively, 3-dimensional) geometry, to find the reflection of a point drop a perpendicular from the point to the line (plane) used for reflection, and extend it the same distance on the other side. Construction Point Q is the reflection of point P through the line AB. Some mathematicians use " flip" as a synonym for "reflection". Typically, however, unqualified use of the term "reflection" means reflection in a hyperplane. Other examples include reflections in a line in three-dimensional space. In a Euclidean vector space, the reflection in the point situated at the origin is the same as vector negation. This operation is also known as a central inversion ( Coxeter 1969, §7.2), and exhibits Euclidean space as a symmetric space. For instance a reflection through a point is an involutive isometry with just one fixed point the image of the letter p under it Such isometries have a set of fixed points (the "mirror") that is an affine subspace, but is possibly smaller than a hyperplane. The term reflection is sometimes used for a larger class of mappings from a Euclidean space to itself, namely the non-identity isometries that are involutions. ![]() A reflection is an involution: when applied twice in succession, every point returns to its original location, and every geometrical object is restored to its original state. Its image by reflection in a horizontal axis (a horizontal reflection) would look like b. For example the mirror image of the small Latin letter p for a reflection with respect to a vertical axis (a vertical reflection) would look like q. The image of a figure by a reflection is its mirror image in the axis or plane of reflection. In mathematics, a reflection (also spelled reflexion) is a mapping from a Euclidean space to itself that is an isometry with a hyperplane as a set of fixed points this set is called the axis (in dimension 2) or plane (in dimension 3) of reflection. For reflexivity of binary relations, see reflexive relation. And then you can see that indeed do they indeed do look like reflections flipped over the X axis.This article is about reflection in geometry. And this bottom part of the quadrilateral gets reflected above it. So you an kind of see this top part of the quadrilateral And what's interesting about this example is that, the original quadrilateral is on top of the X axis. We have constructed the reflection of ABCD across the X axis. And we'll keep our XĬoordinate of negative two. Unit below the X axis, we'll be one unit above the X axis. If we reflect across the X axis instead of being one And so let's see, D right now is at negative two comma negative one. So this goes to negative five, one, two, three, positive four. So it would have theĬoordinates negative five comma positive four. Units below the X axis, it will be four units above the X axis. The same X coordinate but instead of being four C, right here, has the X coordinate of negative five. The same X coordinate but it's gonna be two I'm having trouble putting the let's see if I move these other characters around. So let's make this right over here A, A prime. So, its image, A prime we could say, would be four units below the X axis. So we're gonna reflect across the X axis. So let's just first reflect point let me move this a littleīit out of the way. Move this whole thing down here so that we can so that we can see what is going on a little bit clearer. So we can see the entire coordinate axis. And we need to construct a reflection of triangle A, B, C, D. ![]() Tool here on Khan Academy where we can construct a quadrilateral. Asked to plot the image of quadrilateral ABCD so that's this blue quadrilateral here.
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