The eccentricity of the hyperbola 16x2 – 9y2 = 1 is

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  1. \(\frac{3}{5}\)
  2. \(\frac{5}{3}\)
  3. \(\frac{4}{5}\)
  4. \(\frac{5}{4}\)

Answer (Detailed Solution Below)

Option 2 : \(\frac{5}{3}\)
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Detailed Solution

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Concept:

Hyperbola: The locus of a point which moves such that its distance from a fixed point is greater than its distance from a fixed straight line. (Eccentricity = e > 1)

Equation

\(\frac{{\;{{\bf{x}}^2}}}{{{{\bf{a}}^2}}} - \frac{{{{\bf{y}}^2}}}{{{{\bf{b}}^2}}} = 1\)

\(- \frac{{\;{{\bf{x}}^2}}}{{{{\bf{a}}^2}}} + \frac{{{{\bf{y}}^2}}}{{{{\bf{b}}^2}}} = 1\)

Equation of Transverse axis

y = 0

x = 0

Equation of Conjugate axis

x = 0

y = 0

Length of Transverse axis

2a

2b

Length of Conjugate axis

2b

2a

Vertices

(± a, 0)

(0, ± b)

Focus

(± ae, 0)

(0, ± be)

Directrix

x = ± a/e

y = ± b/e

Centre

(0, 0)

(0, 0)

Eccentricity

\(\sqrt {1 + {\rm{\;}}\frac{{{{\rm{b}}^2}}}{{{{\rm{a}}^2}}}}\)

\(\sqrt {1 + {\rm{\;}}\frac{{{{\rm{a}}^2}}}{{{{\rm{b}}^2}}}}\)

Length of Latus rectum

\(\frac{{2{{\rm{b}}^2}}}{{\rm{a}}}\)

\(\frac{{2{{\rm{a}}^2}}}{{\rm{b}}}\)

Focal distance of the point (x, y)

ex ± a

ey ± a

 

Calculation:

Given:

16x2 – 9y2 = 1

\( \Rightarrow \frac{{{\rm{\;}}{{\rm{x}}^2}}}{{\frac{1}{{16}}}} - \frac{{{{\rm{y}}^2}}}{{\frac{1}{9}}} = 1\)

Compare with \(\frac{{{\rm{\;}}{{\rm{x}}^2}}}{{{{\rm{a}}^2}}} - \frac{{{{\rm{y}}^2}}}{{{{\rm{b}}^2}}} = 1\)

∴ a2 = 1/16 and b2 = 1/9

Eccentricity = \(\sqrt {1 + {\rm{\;}}\frac{{{{\rm{b}}^2}}}{{{{\rm{a}}^2}}}} = \;\sqrt {1 + \;\frac{{\left( {\frac{1}{9}} \right)}}{{\left( {\frac{1}{{16}}} \right)}}} = \;\sqrt {1 + \;\frac{{16}}{9}} = \;\sqrt {\frac{{25}}{9}} = \;\frac{5}{3}\) 

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