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JEE Class main Answered

Sir pls solve the following.
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Asked by rsudipto | 05 Jan, 2019, 09:20: AM
answered-by-expert Expert Answer
begin mathsize 18px style straight r subscript 1 comma straight r subscript 2 comma straight r subscript 3...... exradii comma
straight a comma straight b comma straight c space sides space of space increment
straight s equals semiperimeter

straight r equals fraction numerator area increment over denominator straight s end fraction
straight r subscript 1 equals fraction numerator area increment over denominator straight s minus straight a end fraction
straight r subscript 2 equals fraction numerator area increment over denominator straight s minus straight b end fraction
straight r subscript 3 equals fraction numerator area increment over denominator straight s minus straight c end fraction

straight r plus straight r subscript 1 equals straight r subscript 2 plus straight r subscript 3.......... given
fraction numerator area increment over denominator straight s end fraction plus fraction numerator area increment over denominator straight s minus straight a end fraction equals fraction numerator area increment over denominator straight s minus straight b end fraction plus fraction numerator area increment over denominator straight s minus straight c end fraction
1 over straight s plus fraction numerator 1 over denominator straight s minus straight a end fraction equals fraction numerator 1 over denominator straight s minus straight b end fraction plus fraction numerator 1 over denominator straight s minus straight c end fraction
fraction numerator 2 straight s minus straight a over denominator straight s open parentheses straight s minus straight a close parentheses end fraction equals fraction numerator 2 straight s minus straight b minus straight c over denominator open parentheses straight s minus straight b close parentheses open parentheses straight s minus straight c close parentheses end fraction
sub space straight s equals fraction numerator straight a plus straight b plus straight c over denominator 2 end fraction
fraction numerator straight b plus straight c over denominator straight a end fraction equals fraction numerator straight b squared plus straight c squared minus straight a plus 2 bc over denominator negative straight b squared minus straight c squared plus straight a plus 2 bc end fraction
fraction numerator straight b plus straight c over denominator straight a end fraction equals fraction numerator begin display style fraction numerator straight b squared plus straight c squared minus straight a over denominator 2 bc end fraction end style plus 1 over denominator negative open parentheses fraction numerator straight b squared plus straight c squared minus straight a over denominator 2 bc end fraction close parentheses plus 1 end fraction
fraction numerator straight b squared plus straight c squared minus straight a over denominator 2 bc end fraction equals cosA
fraction numerator straight b plus straight c over denominator straight a end fraction equals fraction numerator begin display style 1 plus cosA end style over denominator 1 minus cosA end fraction
componendo
fraction numerator straight a plus straight b plus straight c over denominator straight a end fraction equals fraction numerator begin display style 2 end style over denominator 1 minus cosA end fraction
straight s over straight a equals fraction numerator begin display style 1 end style over denominator 1 minus cosA end fraction
now
straight A greater than straight pi over 3
also space straight A less than straight pi....... straight A thin space is space vertex space of space triangle
so
straight pi over 3 less than straight A less than straight pi
1 half less than cos space straight A less than 0
max space value space of space cos space straight A space equals space 1 half
min space value space of space cos space straight A space equals space minus 1
so space max space value space of space straight s over straight a space equals space fraction numerator begin display style 1 end style over denominator 1 minus begin display style 1 half end style end fraction equals 2
min space value space of space straight s over straight a space equals space fraction numerator begin display style 1 end style over denominator 1 minus open parentheses negative 1 close parentheses end fraction equals 1 half

end style
Answered by Arun | 18 Jan, 2019, 10:24: AM
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