There are many ways to play with angles but for doing things like moulding or wrapping wood around something like in the above picture there is a simple but important difference between saws and the way you define angles in geometry. On a miter saw if you set the angle at 0 degrees it creates a 90 degree angle. A different way to look at it is if you are joining boards end to end like you would with baseboards the angle to set the saw to is half the change direction you want to make. For example the corner in the picture above has 2 turns making a 90 degree total change in direction. Each turn is 45 degrees so the saw gets set to 22.5 degrees each way.