Plotting heading between two points in x-y plane - iphone

Question

I'm trying to implement a small radar that plots targets based on latitude and longitude coordinates similar to the radar in the Layar AR iPhone app. I have the compass and locationManager working to get the lat/lon, heading and distance between two points. However I'm having trouble plotting the points onto the x-y plane. Could you point me in the right direction(so-to-speak)?
This is the method that I am using to plot but the results are not correct:
-(void) addTargetIndicatorWithHeading:(float)heading andDistance:(float)distance{
//draw target indicators
//need to convert radians and distance to cartesian coordinates
float radius = 50;
float x0 = 0.0;
float y0 = 0.0;
//convert heading from radians to degrees
float angle = heading * (180/M_PI);
//x-y coordinates
float x1 = (x0 + radius * sin(angle));
float y1 = (y0 + radius * cos(angle));
TargetIndicator *ti = [[TargetIndicator alloc] initWithFrame:CGRectMake(x1, y1, 5, 5)];
[self addSubview:ti];
[ti release];
}

Answer 1

I guess the problem lies within the present view's origin coordinate not being added to ur coordinate.
just modify your x1 and y1 by adding the origin.x and origin.y of the current view to which you add ti as a subview.

Answer 2

I figured out what was wrong but I'm don't know the reasoning behind it. First I should not have been converting the radians to degrees. This gives me the correct positioning but it is rotated 180 degrees. So to fix it, I subtract the radians from PI.
Here is the solution:
-(void) addTargetIndicatorWithHeading:(float)heading andDistance:(float)distance{
//draw target indicators
//need to convert radians and distance to cartesian coordinates
float radius = 50;
//origin offset
float x0 = 50.0;
float y0 = 50.0;
//convert heading from radians to degrees and rotate by 180 deg
float angle = M_PI - heading;
float x1 = (x0 + radius * sin(angle));
float y1 = (y0 + radius * cos(angle));
TargetIndicator *ti = [[TargetIndicator alloc] initWithFrame:CGRectMake(x1, y1, 5, 5)];
[self addSubview:ti];
[ti release];
}