![]() Unlike the axis, its points are not fixed themselves. The plane of rotation is a plane that is invariant under the rotation.The axis of rotation is a line of its fixed points.The rotation group is a point stabilizer in a broader group of (orientation-preserving) motions. This (common) fixed point or center is called the center of rotation and is usually identified with the origin. The rotation group is a Lie group of rotations about a fixed point. These two types of rotation are called active and passive transformations. For example, in two dimensions rotating a body clockwise about a point keeping the axes fixed is equivalent to rotating the axes counterclockwise about the same point while the body is kept fixed. But in mechanics and, more generally, in physics, this concept is frequently understood as a coordinate transformation (importantly, a transformation of an orthonormal basis), because for any motion of a body there is an inverse transformation which if applied to the frame of reference results in the body being at the same coordinates. All rotations about a fixed point form a group under composition called the rotation group (of a particular space). Rotation can have a sign (as in the sign of an angle): a clockwise rotation is a negative magnitude so a counterclockwise turn has a positive magnitude.Ī rotation is different from other types of motions: translations, which have no fixed points, and (hyperplane) reflections, each of them having an entire ( n − 1)-dimensional flat of fixed points in a n- dimensional space. It can describe, for example, the motion of a rigid body around a fixed point. Any rotation is a motion of a certain space that preserves at least one point. Rotation in mathematics is a concept originating in geometry. Rotation of an object in two dimensions around a point O. JSTOR ( February 2014) ( Learn how and when to remove this template message). ![]() Unsourced material may be challenged and removed.įind sources: "Rotation" mathematics – news Please help improve this article by adding citations to reliable sources. Note that PC=PC', for example, since they are the radii of the same circle.)Ī positive angle of rotation turns a figure counterclockwise (CCW),Īnd a negative angle of rotation turns the figure clockwise, (CW).This article needs additional citations for verification. (The dashed arcs in the diagram below represent the circles, with center P, through each of the triangle's vertices. A rotation is called a rigid transformation or isometry because the image is the same size and shape as the pre-image.Īn object and its rotation are the same shape and size, but the figures may be positioned differently.ĭuring a rotation, every point is moved the exact same degree arc along the circleĭefined by the center of the rotation and the angle of rotation. Rays drawn from the center of rotation to a point and its image form an angle called the angle of rotation. When working in the coordinate plane, the center of rotation should be stated, and not assumed to be at the origin. A rotation of θ degrees (notation R C,θ ) is a transformation which "turns" a figure about a fixed point, C, called the center of rotation.
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