3.Trigonometrical Ratios, Functions and Identities
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यदि दो वृत्तों के चापों की लंबाई समान हो और वे अपने केंद्र पर क्रमश: $65^{\circ}$ तथा $110^{\circ}$ का कोण बनाते हैं, तो उनकी त्रिज्याओं का अनुपात ज्ञात कीजिए।

A

$22: 13$

B

$22: 13$

C

$22: 13$

D

$22: 13$

Solution

Let $r_{1}$ and $r_{2}$ be the radii of the two circles. Given that

${{\theta _1} = {{65}^\circ } = \frac{\pi }{{180}} \times 65 = \frac{{13\pi }}{{36}}\,{\text{ radian }}}$

and    ${{\theta _2} = {{110}^\circ } = \frac{\pi }{{180}} \times 110 = \frac{{22\pi }}{{36}}{\text{ }}\,{\text{radian }}}$

Let $l$ be the length of each of the arc. Then $l=r_{1} \theta_{1}=r_{2} \theta_{2},$ which gives

$\frac{13 \pi}{36} \times r_{1}=\frac{22 \pi}{36} \times r_{2}, \text { i.e., } \frac{r_{1}}{r_{2}}=\frac{22}{13}$

Hence     $r_{1}: r_{2}=22: 13$

Standard 11
Mathematics

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