The lengths of the intercepts made by a circle $\mathrm{S}$ on $\mathrm{X}$ and $\mathrm{Y}$ - axes are…

The lengths of the intercepts made by a circle $\mathrm{S}$ on $\mathrm{X}$ and $\mathrm{Y}$ - axes are $\frac{2 \sqrt{13}}{3}$ and $\frac{2 \sqrt{22}}{3}$ respectively. If the radius of the circle $\mathrm{S}$ is $\frac{\sqrt{38}}{3}$ and its centre $\mathrm{C}$ lies in the second quadrant, then $\mathrm{C}=$
  1. $\left(\frac{-5}{3}, \frac{4}{3}\right)$
  2. $\left(\frac{-4}{3}, \frac{5}{3}\right)$
  3. $\left(\frac{-6}{5}, \frac{7}{5}\right)$
  4. $\left(\frac{-7}{5}, \frac{6}{5}\right)$

Solution

Let equation of the circle be $x^2+y^2+2 g x+2 f y+c=0$ ... (i) Now length of intercepts made by $\mathrm{x}$ axis is $2 \sqrt{\mathrm{g}^2-\mathrm{c}}=\frac{2 \sqrt{13}}{3} \Rightarrow \mathrm{g}^2-\mathrm{c}=\frac{13}{9}$ ... (ii) Similarly, $2 \sqrt{\mathrm{f}^2-\mathrm{c}}=\frac{2 \sqrt{22}}{3} \Rightarrow \mathrm{f}^2-\mathrm{c}=\frac{22}{9}$ ... (iii) $\text { Since, radius }=\frac{\sqrt{38}}{3}$ $\begin{aligned} & \Rightarrow \sqrt{\mathrm{g}^2+\mathrm{f}^2-\mathrm{c}}=\frac{\sqrt{38}}{3} \Rightarrow \mathrm{g}^2+\mathrm{f}^2-\mathrm{c}=\frac{38}{9} \\ & \Rightarrow \frac{13}{9}+\frac{22}{9}+\mathrm{C}=\frac{38}{9} \quad \text { (by (ii) & (iii)) } \\ & \Rightarrow \mathrm{C}=\frac{3}{9}=\frac{1}{3} \end{aligned}$ So $\mathrm{g}^2=\frac{13}{9}+\frac{1}{3}=\frac{16}{9} \Rightarrow \mathrm{g}= \pm \frac{4}{3}$ $\& \mathrm{f}^2=\frac{22}{9}+\frac{1}{3}=\frac{25}{9} \Rightarrow \mathrm{f}= \pm \frac{5}{3}$ Since centre lies in 2nd quadrant so centre $=\left(-\frac{4}{3}, \frac{5}{3}\right)$

Asked in: AP EAMCET 2023 (16 May Shift 2)

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