function cosh( x ) {
	return addon( x );
}
Computes the hyperbolic cosine of a double-precision floating-point number.

@private
@param {number} x - input value
@returns {number} hyperbolic cosine

@example
var v = cosh( 0.0 );
// returns 1.0

@example
var v = cosh( 2.0 );
// returns ~3.762

@example
var v = cosh( -2.0 );
// returns ~3.762

@example
var v = cosh( NaN );
// returns NaN