You can measure an angle between 2 segments. Each segment can be chosen independently from a polyline, a polygon, a rectangle, an "angle" object or a "line" object.

Measure an angle:

1. Select in an image the first segment of annotations and regions of interest by clicking on the left mouse button.
2. In the same image, while holding the 'Shift' key, click again on the left mousse button to select the second segment of annotations and regions of interest.
3. Click on the "2D Actions" button of the 2D Viewer window. A menu will appear under your mouse cursor.
4. Click on "Angle".
5. The measure of the angle has been created.

You can also make the measure of the angle by 2 others methods: by the top menu of the 2D viewer window, or by the context menu.
See "How to launch actions".

To modify the angle value position, see "How to measure or modify an angle".