Prove that a rotation matrix preserves distance

In summary, the conversation discusses proving that a rotation matrix in R3 preserves distance. One participant suggests using a trig representation in R2, while another asks for a more elegant method in R3. The question of what is being used as a definition of "rotation matrix" is also raised.
  • #1
gottfried
119
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Homework Statement


Prove that a rotation matrix in R3 preserves distance.

Such that if A is a 3*3 orthogonal rotation matrix then |A.v|=|v|.

I know one can prove this is in R2 by using a trig representation of a rotation matrix and then simplifying. Is there an analogue method in R3 or some other more elegant way. A hint/push in the right direction would be nice.
 
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  • #2
I am puzzled by the question. What, exactly, are you using as a definition of "rotation matrix". If it is the obvious- that it corresponds to a rotation- the fact that it does not change length follows immediately from the definition of "rotation".
 

FAQ: Prove that a rotation matrix preserves distance

What is a rotation matrix?

A rotation matrix is a mathematical tool used to rotate a coordinate system in a multi-dimensional space. It is represented by a square matrix with a specific structure and is commonly used in geometry, computer graphics, and physics.

How does a rotation matrix preserve distance?

A rotation matrix preserves distance by maintaining the same distance between any two points in the original coordinate system after the rotation is applied. This is because the rotation matrix only changes the orientation of the coordinate system, not the distance between points.

Can you provide an example of a rotation matrix preserving distance?

Yes, for example, if we have a point (3,4) in a coordinate system and we rotate the system by 90 degrees counterclockwise, the new coordinates of the point will be (-4,3). The distance between the original point and the new point remains the same, which is equal to 5 units.

Are there any exceptions where a rotation matrix may not preserve distance?

Yes, there are some special cases where a rotation matrix may not preserve distance. For example, if the rotation is performed around a point that is not the origin, the distance between points may change. Also, in non-Euclidean spaces, the concept of distance may differ, and a rotation matrix may not be applicable.

How is the preservation of distance in a rotation matrix useful?

The preservation of distance in a rotation matrix is useful in many fields, including robotics, computer vision, and navigation. It allows us to accurately represent and manipulate objects in a multi-dimensional space without changing their relative position and distance, which is essential in many applications.

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