Gujarati
10-1.Circle and System of Circles
hard

वृत्त ${x^2} + {y^2} + 2x + 8y - 23 = 0$ और ${x^2} + {y^2} - 4x - 10y + 9 = 0$ की उभयनिष्ठ स्पर्श रेखाओं की संख्या है

A

$1$

B

$3$

C

$2$

D

इनमें से कोई नहीं

Solution

(c) ${x^2} + {y^2} + 2x + 8y – 23 = 0$

$\therefore {C_1}( – 1, – 4),{r_1} = 2\sqrt {10} $

तथा ${x^2} + {y^2} – 4x – 10y + 9 = 0$

${C_2}(2,5),{r_2} = 2\sqrt 5 $

${C_1}{C_2}$ = केन्द्रों के बीच की दूरी  = $\sqrt {9 + 81} $

$= 3\sqrt {10}  = 9.486$

और ${r_1} + {r_2} = 2(\sqrt {10}  + \sqrt 5 ) = 10.6$

${r_1} – {r_2} = 2\sqrt 5 (\sqrt 2  – 1) = 2 \times 2.2 \times 0.4 $

$= 4.4 \times 0.4 = 1.76$

${C_1}{C_2} = 2\sqrt {10}  > {r_1} – {r_2}$

${r_1} – {r_2} < {C_1}{C_2} < {r_1} + {r_2}$

दो स्पर्श रेखायें खींची जा सकती हैं।

Standard 11
Mathematics

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