Exponentiation
Exponentiation is a mathematical operation, written as , involving two numbers, the "base" and the "exponent" . When is a positive integer, exponentiation corresponds to repeated multiplication of the base: that is, is the product of multiplying bases:
Mathematics and the Imagination
Chapter 3 is "Pie (, i, e) Transcendental and Imaginary". To motivate e (mathematical constant), they discuss first compound interest and then continuous compounding. "No other mathematical constant, not even , is more closely connected with human affairs" (p 86).
"[e] has played an integral part in helping mathematicians describe and predict what is for man the most important of all natural phenomena – that of growth."
The exponential function, "y" = e ... "is the only function of "x" with the rate of change with respect to "x" equal to the function itself." (p 87) 
The authors define the Gauss plane and describe the action of multiplication by i as rotation through 90°. They address Euler's identity, i.e. the expression "e" + 1 = 0, indicating that the venerable Benjamin Peirce called it "absolutely paradoxical".
A note of idealism is then expressed: "When there is so much humility and so much vision everywhere, society will be governed by science and not its clever people." (pp 103,4)