Join the Most Relevant JEE Main 2025 Test Series & get 99+ percentile! Join Now
Search any question & find its solution
Question: Answered & Verified by Expert
The sum of the radii of inscribed and circumscribed circles for an $\mathrm{n}$ sided regular polygon of side a, is
MathematicsProperties of TrianglesJEE MainJEE Main 2003
Options:
  • A
    $\frac{a}{4} \cot \left(\frac{\pi}{2 n}\right)$
  • B
    $a \cot \left(\frac{\pi}{n}\right)$
  • C
    $\frac{a}{2} \cot \left(\frac{\pi}{2 n}\right)$
  • D
    $\operatorname{acot}\left(\frac{\pi}{2 n}\right)$
Solution:
2672 Upvotes Verified Answer
The correct answer is:
$\operatorname{acot}\left(\frac{\pi}{2 n}\right)$
$\tan \left(\frac{\pi}{n}\right)=\frac{a}{2 r} ; \sin \left(\frac{\pi}{n}\right)=\frac{a}{2 R}$

$r+R=\frac{a}{2}\left[\cot \frac{\pi}{n}+\operatorname{cosec} \frac{\pi}{n}\right] \Rightarrow r+R=\frac{a}{2} \cdot \cot \left(\frac{\pi}{2 n}\right)$

Looking for more such questions to practice?

Download the MARKS App - The ultimate prep app for IIT JEE & NEET with chapter-wise PYQs, revision notes, formula sheets, custom tests & much more.