Mathematics
Complex Exponential Functions
Quick fact
The complex exponential function e^(iθ) traces out the unit circle in the complex plane, and its special case e^(iπ) + 1 = 0 is often called the most beautiful equation in mathematics.
Why this is interesting
What if an exponential function could spin? You've seen exponential growth and decay, but what happens when the exponent becomes imaginary—a number whose square is negative?