Question 21

If cot^(-1) (3x+5)>π/4, then find the range of the values of x.

 

 

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Question 21 If cot^(โˆ’1) (3๐‘ฅ+5)>๐œ‹/4, then find the range of the values of ๐‘ฅ.Given ใ€–๐‘๐‘œ๐‘กใ€—^(โˆ’1) (3๐‘ฅ+5)>๐œ‹/4 Taking cot^(โˆ’1) on other side, Sign of inequality changes because cot^(โˆ’1) is a decreasing function ๐Ÿ‘๐’™+๐Ÿ“<๐’„๐’๐’•โกใ€–๐…/๐Ÿ’ใ€— Putting ๐‘๐‘œ๐‘กโกใ€–๐œ‹/4ใ€— = 1 3๐‘ฅ+5<1 3๐‘ฅ<1โˆ’5 3๐‘ฅ<โˆ’4 Note: Here cot^(โˆ’1) is a decreasing function. This means As x increases cot^(โˆ’1) decreases For example ใ€–๐’„๐’๐’•ใ€—^(โˆ’๐Ÿ) โˆš๐Ÿ‘<ใ€–๐’„๐’๐’•ใ€—^(โˆ’๐Ÿ) ๐Ÿ as 30ยฐ < 45ยฐ But, if we remove ใ€–๐’„๐’๐’•ใ€—^(โˆ’๐Ÿ) โˆš๐Ÿ‘>๐Ÿ So, when we remove cot^(โˆ’1), we have to change the sign of inequality ๐’™<(โˆ’๐Ÿ’)/๐Ÿ‘ So, ๐’™ โˆˆ(โˆ’โˆž,(โˆ’๐Ÿ’)/๐Ÿ‘)

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo