1. The problem statement, all variables and given/known data On a X-Y plane we have a square with its 4 corners A(3,1) B(7,3) C(2,6) D(0,2). We are to rotate the rest of the square around the point A clockwise by 70 degrees. 2. Relevant equations (I am not sure how they are called in English) The rotation matrix 2x2 1st row: cosa ,-sina 2nd row: sina, cosa - call it G(a) so that X' = G(a) * X 3. The attempt at a solution I know how to use this matrix transposition or conversion (not sure how it is called) when I am rotating a vector around the 0-point, but I don't know how to rotate a vector around a point on the plane. EDIT: Just as I posted this I got a revelation - I will Rotate the vector AB using the rotation matrix and then add point A's x and y coordinate respectively to the product of the matrixes. And all the same with the other corners - construct vector AC AD and deja vu. Now there is a question: When I do the product of G(a) * A , where A is the vector matrix - the vector spins counterclockwise, but when I do the product of AT * G(a) - the vector spins clockwise. I don't understand why - does it mean that AT * G(a) = G(-a) * A?