[AmirSavand]

I don't know the math for this, but I have this function which gets in-front of/behind vehicle.

I think this could help, you just need to move this point to left and right 2 times with different distance.

PHP код:

stock GetInFrontOfVehicle(vehicleid, &Float:x, &Float:y, Float:distance)
{
    new Float:a;
    GetVehiclePos(vehicleid, x, y, a);
    GetVehicleZAngle(vehicleid, a);
    x += (distance * floatsin(-a, degrees));
    y += (distance * floatcos(-a, degrees));
}