how to detect touch in a circle - cocos2d-iphone

Question

I really assistance. Im a little confused.
i have a circle sprite, and this code
-(void)ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
CGSize winSize =[[CCDirector sharedDirector] winSize];
UITouch* myTouch = [touches anyObject];
CGPoint location = [myTouch locationInView: [myTouch view]];
location = [[CCDirector sharedDirector]convertToGL:location];
CCSprite *circleSprite = (CCSprite*)[self getChildByTag:30];
CGRect correctColorSprite1 = [circleSprite boundingBox];
if (CGRectContainsPoint(correctColorSprite1, location)) {
NSLog(#"inside");
}
as i know there is a bounding box, when i touch slightly outside of the top circle it will still detect the touch.
i have read in some forums that i need to detect distance of the centre of the sprite and the touch point. But i really don't know how to write that code. My circle size is around 50 points.
I hope someone can help me out give me some snippets of a improved code to detect the touch only in the circle. Not with the bounding box. Your help is very great full.

Answer 1

Try this:
-(void)ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
CGSize winSize =[[CCDirector sharedDirector] winSize];
UITouch* myTouch = [touches anyObject];
CGPoint location = [myTouch locationInView: [myTouch view]];
location = [[CCDirector sharedDirector]convertToGL:location];
CCSprite *circleSprite = (CCSprite*)[self getChildByTag:30];
//CGRect correctColorSprite1 = [circleSprite boundingBox];
CGRect correctColorSprite1 = CGRectMake(
circleSprite.position.x - (circleSprite.contentSize.width/2),
circleSprite.position.y - (circleSprite.contentSize.height/2),
circleSprite.contentSize.width,
circleSprite.contentSize.height);
//find the center of the bounding box
CGPoint center=ccp(correctColorSprite1.size.width/2,correctColorSprite1.size.height/2);
//now test against the distance of the touchpoint from the center
if (ccpDistance(center, location)<50)
{
NSLog(#"inside");
}
}