Thread: Finding a point position on a shape after the shape was rotated

Hi. First I'd like to let you know that I'm probably in the wrong section, but this is because I really, honestly, don't know where to put this question. If I knew what the problem is about, I'd have looked up on the Internet before asking.

So, I've made a picture explaining my problem : http://i.imgur.com/EkQZq.png .

If anyone can explain me how to solve this kind of problem and tell me what domain it is related to, it would be greatly appreciated.

Thanks already.

This is a standard problem if you allow some changes.
First lets say the center is ; that is your .
Then if the circle most have radius of say five.
The ‘red’ point has well-known coordinates:


If you let then that rotates the point to the point .

Does that help?

Hello, Minikloon!

Another solution . . .

Say I have a circle with center
A point is at
Rotate the circle radians counterclockwise.
Determine the new position of point

Code:

              * * *
          *           *
        *               *
       *                 *
             
      *      4  C         *
      *   + - - o         *
      *   :   *           *
         4: *
       *  o              *
        * P             *
          *           *
              * * *

Point lies on the circle with center and radius

The coordinates of are: .

Originally Posted by Soroban

Hello, Minikloon!
Another solution . . .

Another solution???
Come on, that is identical to the solution that I posted. Is it not?
Please correct me if I am wrong. How is it another solution?

Hello, Plato!

Don't get your shorts in a knot . . . identical?

You made some changes . . . placing the center at the origin.
. . I didn't ... I solved it using the original information.

I believe that even the touchy moderators will agree
. . that I made a significant contribution.