The hyperbolic cosine and hyperbolic sine functions are defined by cosh x = ex + e-x 2
Chapter 9, Problem 80(choose chapter or problem)
The hyperbolic cosine and hyperbolic sine functions are defined by cosh x = ex + e-x 2 and sinh x = ex - e-x 2 . Prove that (cosh x) 2 - (sinh x) 2 = 1.
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