I personally like the looks of a well crafted miter joint. OK purists, I know that there are stronger joints but in my case, I use them where they are strong enough for the intended purpose. In order to produce an appealing miter joint, one needs to understand the relationship between the error in cutting a 45 degree with your favorite tool and the resulting gap in the assembled miter joint. In reality, one might decide what kind of gap is acceptable (1/64", 1/32", ...) and then ask how accurately must my tool be set up to achieve that gap. The attached document presents the equations that relate the gap error and the angle error. For the math challenged, you can still use the equations that are given without understanding the gory details.
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