Lessons.GregGoad.net
Trigonometry is the crux of applied mathematics. It is used in a massive amount of disciplines: from astronomy, to engineering, to surveying. The reason it is so prevalent is how immensely useful it is. What trigonometry lets you do is to take one set of measurements and extrapolate that to an entire other set of measurements.
Trigonometry is based on the mathematics of circles and ratios. It can be tough to calculate the actual values by hand; in most applied settings you will be using a calculator to calculate the values for you; in that regard, trigonometry can be easy. You still have to be able to tell which button to press, though, and that takes study and practice. Beyond that, the field of trigonometry keeps going and going.