Check user inside Map Circle and activate a button

Question

I am developing an application and I came across a logic that I am not able to solve, if someone can give a strength I would appreciate it very much.

I have a destiny that has a range circle of it I made it with this code:

private void setDestino(Double latitude, Double longitude){
    latDestino = latitude;
    longDestino = longitude;
    LatLng destino = new LatLng(latDestino, longDestino);
    map.addMarker(new MarkerOptions().position(destino).title  ("Destino entrega Depósito."));
    CircleOptions circle = new CircleOptions().center(destino);
    circle.fillColor(Color.LTGRAY);
    circle.radius(30); //Em metros.
    map.addCircle(circle);
}

and I have a marker from a user who is going to that destination, he is being updated by picking up the location information from the mobile:

@Override
public void onLocationChanged(Location l) {
    if(l != null){
        latitude = l.getLatitude();
        longitude = l.getLongitude();
        LatLng usuario= new LatLng(latitude, longitude);
        LatLng destino = new LatLng(latDestino, longDestino);
        map.clear();
        map.addMarker(new MarkerOptions().position(usuario).title("Usuário"));
        map.moveCamera(CameraUpdateFactory.newLatLng(usuario));
        setDestino(latDestino, longDestino);
        adicionaPolyline(map, mastertrack, destino);
    }
    map.animateCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(l.getLatitude(), l.getLongitude()), 20));

}

The logic I lack is, when the user is outside the circle a button will be disabled, when I click on the target circle I check if the user marker is inside the circle and activate the button.

If anyone knows and can clarify this logic it will be a great favor. Thank you.