User talk:Liartar~enwiki

Part of the problem is that you can't really see the relationship between the point and its image under the rotation from your diagram. You have only labelled one point ("P"). This point does not have coordinates (x,y) since it does not lie on the vertical line at x. So I am not sure what this point is in relation to the rotation. The highest point in your diagram would have first coordinate xcos θ + ysin θ in the new coordinate system, but it is not the image of the point P under a rotation of angle θ about the origin.
 * The usual verification starts with a point P with coordinates (rCos ψ, rSin ψ), where r is the distance from P to the origin O and ψ the angle that the line OP makes with the positive x-axis. After rotating by an angle θ about the origin (counterclockwise), the new coordinates of the image P' are (rCos (ψ + θ), rSin (ψ + θ)). Here r stays the same since P and P' are at the same distance from the origin, only the angle made with the positive x-axis changes. Using the addition rule for Sin and Cos, you can simplify the expressions for the new coordinates and write them in terms of the old coordinates. The signs between terms in these expressions come from the addition rules. This can all be done geometrically, using congruent and/or similar right triangles, but this just amounts to providing a geometric proof of the addition rules for the trig functions. I hope this helps. Bill Cherowitzo (talk) 15:46, 16 March 2013 (UTC)
 * When we talk about Euclidean motions, as this section is doing, it is the objects of the plane which move with respect to a fixed coordinate axis system. What you are proposing to do, rotate the coordinate axes, is called a change of basis and is not considered a motion of the plane, just a change in the point of view. You are correct in saying that the change of basis formula and the rotation formula are not the same. If you do a counterclockwise change of basis, in order to see the original coordinates you would have to do a clockwise rotation, as you observed. Bill Cherowitzo (talk) 04:47, 17 March 2013 (UTC)

Your account will be renamed
Hello,

The developer team at Wikimedia is making some changes to how accounts work, as part of our on-going efforts to provide new and better tools for our users like cross-wiki notifications. These changes will mean you have the same account name everywhere. This will let us give you new features that will help you edit and discuss better, and allow more flexible user permissions for tools. One of the side-effects of this is that user accounts will now have to be unique across all 900 Wikimedia wikis. See the announcement for more information.

Unfortunately, your account clashes with another account also called Liartar. To make sure that both of you can use all Wikimedia projects in future, we have reserved the name Liartar~enwiki that only you will have. If you like it, you don't have to do anything. If you do not like it, you can pick out a different name. If you think you might own all of the accounts with this name and this message is in error, please visit Special:MergeAccount to check and attach all of your accounts to prevent them from being renamed.

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Sorry for the inconvenience.

Yours, Keegan Peterzell Community Liaison, Wikimedia Foundation 01:21, 20 March 2015 (UTC)

Renamed
 This account has been renamed as part of single-user login finalisation. If you own this account you can |log in using your previous username and password for more information. If you do not like this account's new name, you can choose your own using this form after logging in: . -- Keegan (WMF) (talk) 15:25, 22 April 2015 (UTC)