Translations:Two orthogonal sets of circles/17/en

${\begin{aligned}&\mathrm {sinh} ^{\rm {2}}\ at{\rm {+}}{\frac {\rm {1}}{{\rm {sin}}^{\rm {2}}{\theta }_{\rm {1}}}}{\ =\ }{\rm {cosh}}^{\rm {2}}\ {\textit {at}}-{\frac {\rm {1}}{{\rm {tan}}^{\rm {2}}{\theta }_{\rm {1}}}},\end{aligned}}$

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