10-1.Circle and System of Circles
hard

यदि वृत्त $x^2+y^2-2 x+y=5$ के बिंदुओं $P$ तथा $Q$ पर स्पर्श रेखाएँ बिंदु $\mathrm{R}\left(\frac{9}{4}, 2\right)$ पर मिलती हैं, तो त्रिभुज $\mathrm{PQR}$ का क्षेत्रफल है

A

$\frac{13}{4}$

B

$\frac{13}{8}$

C

$\frac{5}{4}$

D

$\frac{5}{8}$

(JEE MAIN-2023)

Solution

Equation of circle is $x^2+y^2-2 x+y-5=0$

$R=\frac{5}{2}$

Length of $P R=Q R=\sqrt{S_1}$

$=\sqrt{\frac{81}{16}+4-\frac{2 \times 9}{4}+2-5}=\frac{5}{4}$

Area of triangle $PQR =\frac{ RL ^3}{ R ^2+ L ^2}=\frac{\frac{5}{2} \cdot \frac{125}{64}}{\frac{25}{4}+\frac{25}{16}}=\frac{5}{8}$

Standard 11
Mathematics

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