Hello!
I'm trying to figure out how to calculate the resultant polar coordinates of a triangle following the triangle's 45 degree rotation about it's own center of mass. I've seen how to rotate the triangle using:

In 2D, you make (X,Y) from (x,y) with a rotation by angle t so:
X = x cos t - y sin t
Y = x sin t + y cos t

... but this only rotates the triangle with regards to the background. I want to figure out a way to find the NEW polar coordinates of the triangle after a 45 degree rotation. Any and all suggestions/comments are welcome!

Joaquin