The length of the latus rectum of the parabola \(169\left\{(x-1)^2+(y-3)^2\right\}=(5 x-12 y+17)^2\) is

The length of the latus rectum of the parabola \(169\left\{(x-1)^2+(y-3)^2\right\}=(5 x-12 y+17)^2\) is
  1. \(\frac{14}{13}\)
  2. \(\frac{12}{13}\)
  3. \(\frac{28}{13}\)
  4. \(\frac{56}{13}\)

Solution

Given parabola, \(\begin{array}{cc} & 169\left[(x-1)^2+(y-3)^2\right]=(5 x-12 y+17)^2 \\ \Rightarrow & (x-1)^2+(y-3)^2=\left(\frac{5 x-12 y+17}{13}\right)^2 \\ \Rightarrow & (S P=P M) \end{array}\) Here, focus is \(S(1,3)\) and directrix \((5 x-12 y+17)=0\) \(\therefore\) Distance of focus from directrix \(\begin{aligned} & \Rightarrow \quad 2 a=\left|\frac{5-36+17}{\sqrt{25+144}}\right| \\ & \Rightarrow \quad 2 a=\frac{14}{13} \\ & \therefore \text { Latusrectum }=4 a=\frac{28}{13} \end{aligned}\)

Asked in: AP EAMCET 2020 (17 Sep Shift 1)

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