How to cut angles when using a miter saw?
Cut Angles with a Miter Saw
1.  Set up the miter saw for angled cuts by adjusting the saw's fence and angle stops.
2.  Place a straightedge guide against the fence, making sure it is parallel to the blade of the saw.
3.  Cut the workpiece at the desired angle, following the line of the guide.
4.  Use a combination square or protractor to measure the angle between the two faces of the workpiece before cutting.