Hyperbolic trigonometry

When u = a cosh x, v = a sinh x, then u2 -v2 = a2 which is the equation for a hyperbola. In other words, the hyperbolic functions in the parametric equations u = a cosh x,v = a sinh x have the same relation to the hyperbola u2 -v2 = a2 that the equations u = a cos 9, v = a sin 9 have to the circle u2 + v2 = a2. 

Inverse Hyperbolic Functions If x = sinh y, then y is the inverse hyperbolic sine of x written y = sinh-1 x or arcsinh x. sinh-1 x = 

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