Aspect ratio rotation issue

//Set X and Y with:
/*
* I iterate through every vertex of an entity
* transformResults is the the std::vector<VERTEX> that holds the entities vertices after adding in regular transforms
*/
float dRotation = Entity::rotation * (M_PI / 180);
newVertX = cos(dRotation) * (transformResults.at(x).X - Entity::centerPoint.X) - sin(dRotation) * (transformResults.at(x).Y - Entity::centerPoint.Y) + Entity::centerPoint.X

newVertY = sin(dRotation) * (transformResults.at(x).X - Entity::centerPoint.X) + cos(dRotation) * (transformResults.at(x).Y - Entity::centerPoint.Y) + Entity::centerPoint.Y