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Revision difference : unit hyperbola
Version 3 Version 2
The {\em unit hyperbola} (cf. the unit circle) is the special case The {\em unit hyperbola} (cf. the unit circle) is the special case
$$x^2-y^2 = 1$$ $$x^2-y^2 = 1$$
of the hyperbola of the hyperbola
$$\frac{x^2}{a^2}-\frac{y^2}{b^2} = 1$$ $$\frac{x^2}{a^2}-\frac{y^2}{b^2} = 1$$
where both the transversal semiaxis $a$ and the conjugate semiaxis $b$ have the length equal to 1. \,The unit hyperbola is rectangular (i.e. the asymptotes \,$x^2-y^2 = 0$\, are at right angles to each other). where both the transversal semiaxis $a$ and the conjugate semiaxis $b$ have the length equal to 1. \,The unit hyperbola is rectangular (i.e. the asymptotes are at right angles to each other).
The unit hyperbola has the well-known parametric representation The unit hyperbola has the well-known parametric representation
$$x = \pm\cosh{t}, \quad y = \sinh{t},$$ $$x = \pm\cosh{t}, \quad y = \sinh{t},$$
also a trigonometric also a trigonometric
$$x = \sec{t}, \quad y = \tan{t}$$ $$x = \sec{t}, \quad y = \tan{t}$$
and a rational parametric representation and a rational parametric representation
$$x = \frac{t^2-1}{2t}, \quad y = \frac{t^2+1}{2t}.$$ $$x = \frac{t^2-1}{2t}, \quad y = \frac{t^2+1}{2t}.$$