How to rotate a vertex around a certain point?

Question

Imagine you have two points in 2d space and you need to rotate one of these points by X degrees with the other point acting as a center.

float distX = Math.a         


        

Answer 1

1. Translate "1" to 0,0

2. Rotate

   x = sin(angle) * r; y = cos(angle) * r;

3. Translate it back