<math>{x^2 \over a^2} + {y^2 \over b^2}  {z^2 \over c^2}=1</math>  (hyperboloid of one sheet), 
or
<math>{x^2 \over a^2} + {y^2 \over b^2}  {z^2 \over c^2}=1</math>  (hyperboloid of two sheets). 
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