So I need help with my home assignment. I would have to rotate a tetragon from one point.
Tetragon is given with letters ABCD. A=(3;1), B=(7;3), C=(2;6) and D=(0;2). I have to rotate the tetragon 70 degrees clockwise from point A using matrices.
Because English is not my first language it's a bit hard for me to understand all the explanations, so the more simplified it would be, the better.
Thanks in advance!
Because matrices represent a linear transformation, they keep the origin point fixed. So you have to make the origin the point you're rotating about. Here, you are rotating from point A, so you need to write the tetragon with point $A'$ being at $(0,0)$. You can do this by subtracting $(3,1)$ from every coordinate.
Then, you can apply the rotation matrix to each point with $\theta = 290^\circ$.
And then "undo' the subtraction of $(3,1)$ by adding back $(3,1)$ to every point.