OS X's search tool, Spotlight, does more than just file and web searches. The handy utility also can be used to do semi-complex math equations with the answers appearing within the results section of the app.
To use Spotlight for math, just open the utility by selecting the magnifying glass icon on the right side of the menu bar or typing Command-Space on the keyboard. Type in your equation using the standard math symbols (+, -, *, /) and brackets. Spotlight automatically produces the answer in the results section, and you can easily copy it using Command-C.
Spotlight supports constants like pi (type in pi) and advanced math functions such as square root (type sqrt), sine (sin), cosine (cos) and tangent (tan). If you use a function, you must type the function name and follow that with the number inside parentheses. For example, the square root of 49 would be entered as sqrt(49). If you need more than Spotlight's basic math, you also can hit enter after you type in your equation to launch the calculator.
If you have any other Spotlight tips, please share them in the comments.