Why Learn Math?
You don't need a Ph.D. in mathematics to be a successful woodworker, but it does help to have a basic math background in one area that seems to cause considerable mathematical frustration - calculating angles. Not understanding the math behind angles puts an unnecessary limitation on your creativity and can lead you into the frustrating, wasteful practice of "calculation" by trial and error. Fortunately, getting comfortable with angle calculations isn't all that difficult, and once you have a few basic concepts and strategies down, you'll be able to tackle any angle problem that comes along.
Angle Math and Tools
Getting a handle on the angle math that comes up in woodworking is a step toward making your woodworking more precise, but the other half the battle is getting the your calculations to work out in the real world. Even if you're able to calculate the most complicated conjunctions of angled parts without working up a sweat, it won't do you much good if your saw's meter gauge promises you one angle and gives you another, or the 90 degree corner you're fitting with crown molding turns out to be 91-1/2 degrees.
To make sure the time you spend working out the math doesn't go to waste it's necessary to have tools that give you marking and measuring precision that matches the accuracy of your calculations. Using precision angle finders and guides will help ensure that your angle cuts are exactly what they're supposed to be and that the angle readings you take are accurate down to fractions of a degree, and rules with micro-fine guide holes will help make sure you get your angle cuts in the right place.
If you're still marking all your cuts with a tape measure and trusting your miter saw to tell you where to find 22-1/2 degrees, it might be time to take a look at Rockler's marking and measuring categories to see what's available in precision tools that will help you bring you woodworking accuracy up to par.