A) \[10\sqrt{2}\]
B) 5
C) \[5\sqrt{2}\]
D) 20
Correct Answer: D
Solution :
\[\because \] Distance between directrices \[=\frac{2a}{e}\]. \[\because \] Eccentricity of rectangular hyperbola \[=\sqrt{2}\]. \ Distance between directrics \[=\frac{2a}{\sqrt{2}}\]. Given that , \[\frac{2a}{\sqrt{2}}=10\]Þ \[2a=10\sqrt{2}\] Now, distance between foci \[=2ae=(10\sqrt{2})\,(\sqrt{2})=20.\]
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