# drawing orientation axes of a rotated bounding box

I have an object from which I extract the contours and as consequence the minimum rotated bounding box. From the latter I can successfully obtain the center point (i.e. **Point(box.center.x, box.center.y)**) and the angle (i.e. **box.angle**) of the box, respectively. Now I want to draw the new orientation axes of the rotated box. In order to achieve that I followed the following formula:

```
x2 = x1 + length * cos(θ)
y2 = y1 + length * sin(θ)
```

where θ should be in radians (right?), **box.angle** provides the angle already in radians, isn't that right? So, there is not need to make the following transformation:

```
θ = angle * 3.14 / 180.0
```

However, doing the following:

```
int length = 150;
Point p1 = Point(box.center.x, box.center.y);
Point p2;
p2.x = (int)round(p1.x + length * cos(angle));
p2.y = (int)round(p1.y + length * sin(angle));
line(img, p1, p2, CV_RGB(0, 255, 0));
```

does not give the correct result for the new x-axis. What am I missing, can someone provide me with a hint. Thanks in advance ;-)

y points

downin opencv ((0,0) is top-left)