A miter saw is a wonderful piece of machinery. The ability it has to cut wood at any angle is a boon to do-it-yourselfers when fitting a piece of molding into a tight corner or creating an angled brace. But perhaps something is hindering your ability to cut--leaving the saw's gauge with a limited range of motion. Learn how to get around the problem and cut an obtuse angle.
Set your miter saw to cut at an acute angle and it will cut at an obtuse angle by default.
Determine which acute angle complements the obtuse angle.
Imagine cutting an obtuse angle of 120 degrees as an example.
Note that miter saw gauges don't go to 60.
Set your saw at 30 (90 - 30 = 60) to cut at a 60-degree angle.
Don't bang the saw down onto whatever you are cutting. Doing so could damage the blade. Move it smoothly and steadily to make a clean cut.
Make sure you are wearing goggles or some other eye protection when using power tools. Always keep your fingers clear of the blade when it is moving.