Hey. I need help with this problem. I am supposed to rotate an equation two different ways: by using the invariant method, and by using the method with formulas (x= x`cosų - y`sinų etc) The answers are supposed to come out the same, but they are not. I'm having problems with the formula method. The cross product term is supposed to be eliminated but I still have it by the end. Can you take a look at my work and see where I went wrong?
(Sorry the picture's so hard to read. It was the best I could do in a short amount of time.)