Khan Academy on a Stick
Hyperbolic trig functions
Motivation and understanding of hyperbolic trig functions.

Hyperbolic Trig Function Inspiration
Exploring a motivation for even defining hyperbolic sine and cosine

Hyperbolic Trig Functions and the Unit Hyperbola
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Why they are called hyperbolic trigonometric functions
Intro to hyperbolic trigonometric functions
You know your regular trig functions that are defined with the help of the unit circle. We will now define a new class of functions constructed from exponentials that have an eery resemblance to those classic trig functions (but are still quite different).