Here is the code for getting points around a circle.

Circle.m

static CGPoint convertRadianToCGPoint( double angle, double length, CGPoint center ) {
    double xCoord = length * cos( angle );
    if( angle == M_PI ) {
        xCoord = -length;
    }

    double yCoord = length * sin( angle );
    if( angle == (3 * M_PI)/2 ){
        yCoord = -length;
    }
    
    return CGPointMake( center.x - xCoord, center.y - yCoord );
}

typedef void (^pointPositionSetter)(int pointID, CGPoint position);

void arrangeNPointsInACircle(int n, CGRect bounds, pointPositionSetter setPosition, BOOL asLetters)
{
    int _vertexCount = n;
    CGRect _vertexBounds = bounds;
    BOOL _verticesAsLetters = asLetters;

    double  width   = _vertexBounds.width / 2.;
    double  height  = _vertexBounds.height / 2.;
    
    CGPoint center = CGPointMake( width, height );
    double radius = width / 1.21;
    double startCoord = M_PI / 2;
    double increment = ( 2 * M_PI ) / (double)_vertexCount;
    
    if (_vertexCount == 12 && !_verticesAsLetters) {
        startCoord += increment;
    } else if (_vertexCount == 1) {
        radius = 0;
    }
    
    for ( int vertex=0; vertex < _vertexCount; vertex++ ) {
        double radianCoord = startCoord + ( increment * vertex );
        CGPoint position = convertRadianToCGPoint( radianCoord, radius, center );
        setPosition(vertex+1, position);
    }
}