Example 25 (Supplementary NCERT) - Integrate x root(1 + x - x2) dx

Example 25 (Supplementary NCERT) - Chapter 7 Class 12 Integrals - Part 2
Example 25 (Supplementary NCERT) - Chapter 7 Class 12 Integrals - Part 3
Example 25 (Supplementary NCERT) - Chapter 7 Class 12 Integrals - Part 4
Example 25 (Supplementary NCERT) - Chapter 7 Class 12 Integrals - Part 5 Example 25 (Supplementary NCERT) - Chapter 7 Class 12 Integrals - Part 6 Example 25 (Supplementary NCERT) - Chapter 7 Class 12 Integrals - Part 7 Example 25 (Supplementary NCERT) - Chapter 7 Class 12 Integrals - Part 8 Example 25 (Supplementary NCERT) - Chapter 7 Class 12 Integrals - Part 9

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Question 3 (Supplementary NCERT) ∫1ā–’š‘„ √(1+š‘„āˆ’š‘„^2 ) š‘‘š‘„ ∫1ā–’š‘„ √(1+š‘„āˆ’š‘„^2 ) š‘‘š‘„ We can write it as:- x = A [š‘‘/š‘‘š‘„ (1+š‘„āˆ’š‘„^2 )]+ B x = A [0+1āˆ’2š‘„]+ B x = A [1āˆ’2š‘„]+ B x = "A"āˆ’2"A" š‘„+ B x = āˆ’2"A" š‘„+(š“+šµ) Comparing x and constant term Thus, we can write x = A [1āˆ’2š‘„] + B x = ((āˆ’1)/2)[1āˆ’2š‘„] + 1 x = (āˆ’2A) x š‘„/š‘„ = āˆ’2A 1 = āˆ’2A A = (āˆ’1)/2 0 = A + B B = āˆ’A B = āˆ’((āˆ’1)/2) B = 1/2 Integrating ∫1ā–’ć€–š‘„āˆš(1+š‘„āˆ’š‘„^2 ) 怗 š‘‘š‘„ = ∫1▒〖[(āˆ’1/2)[1āˆ’2š‘„]+1/2] 怗 √(1+š‘„āˆ’š‘„^2 ) š‘‘š‘„ = ∫1▒〖[(āˆ’1/2)[1 āˆ’2š‘„] √(1+š‘„āˆ’š‘„^2 )+1/2 √(1+š‘„āˆ’š‘„^2 )] 怗 š‘‘š‘„ = ∫1▒〖(āˆ’1/2)[1āˆ’2š‘„] √(1+š‘„āˆ’š‘„^2 ) š‘‘š‘„+怗 ∫1▒〖1/2 √(1āˆ’š‘„āˆ’š‘„^2 )怗 š‘‘š‘„ = āˆ’1/2 ∫1▒〖[1āˆ’2š‘„] √(1+š‘„āˆ’š‘„^2 ) š‘‘š‘„+怗 1/2 ∫1ā–’āˆš(1+š‘„āˆ’š‘„^2 ) š‘‘š‘„ Solving š‘°_šŸ I_1 = (āˆ’1)/2 ∫1▒〖[1āˆ’2š‘„] √(1+š‘„āˆ’š‘„^2 )怗 š‘‘š‘„ Let 1 + š‘„ āˆ’ š‘„^2 = t Diff. both sides w.r.t.x 0 + 1 āˆ’2x = š‘‘š‘”/š‘‘š‘„ (1 āˆ’ 2x) dx = dt dx = š‘‘š‘”/(1 āˆ’ 2š‘„) Thus, our equation becomes I_1 = (āˆ’1)/2 ∫1▒〖[1āˆ’2š‘„] √(1+š‘„āˆ’š‘„^2 )怗 š‘‘š‘„ Putting the value if (1+š‘„āˆ’š‘„^2) and dx, we get I_1 = (āˆ’1)/2 ∫1▒〖[1āˆ’2š‘„] āˆšš‘”ć€—. š‘‘š‘„ I_1 = (āˆ’1)/2 ∫1▒〖[1āˆ’2š‘„] āˆšš‘”ć€—. š‘‘š‘”/[1 āˆ’ 2š‘„] š¼_1 = (āˆ’1)/2 ∫1ā–’āˆšš‘”. š‘‘š‘” I_1 = (āˆ’1)/2 ∫1▒〖(š‘”)怗^(1/2) š‘‘š‘” I_1 = (āˆ’1)/2 ć€–š‘” 怗^(1/2 + 1)/((1/2 + 1) )+ C_1 I_1 = (āˆ’1)/2 ć€–š‘” 怗^(3/2 )/((3/2) )+ C_1 I_1 = (āˆ’1)/3 ć€–š‘” 怗^(3/2 )+ C_1 I_1 = (āˆ’1)/3 怖(1āˆ’š‘„ āˆ’š‘„^2 ) 怗^(3/2 )+ C_1 ("Using t = " 1āˆ’š‘„ āˆ’š‘„^2 ) Solving š‘°_šŸ I_2 = 1/2 ∫1ā–’āˆš(1+š‘„āˆ’š‘„^2 ) š‘‘š‘„ I_2 = 1/2 ∫1ā–’āˆš(āˆ’(š‘„^2āˆ’š‘„āˆ’1)) š‘‘š‘„ I_2 = 1/2 ∫1ā–’āˆš(āˆ’[š‘„^2āˆ’2(š‘„)(1/2)āˆ’1] ) š‘‘š‘„ I_2 = 1/2 ∫1ā–’ć€–āˆš(āˆ’[š‘„^2āˆ’2(š‘„)(1/2)+(1/2)^2āˆ’(1/2)^2āˆ’1] ) 怗 š‘‘š‘„ I_2 = 1/2 ∫1ā–’ć€–āˆš(āˆ’[(š‘„āˆ’1/2)^2āˆ’(1/2)^2āˆ’1] ) 怗 š‘‘š‘„ I_2 = 1/2 ∫1ā–’ć€–āˆš(āˆ’[怖 (š‘„āˆ’1/2)怗^2+(āˆ’1 āˆ’4)/4] ) 怗 š‘‘š‘„ I_2 = 1/2 ∫1ā–’ć€–āˆš(āˆ’[怖 (š‘„āˆ’1/2)怗^2 āˆ’5/4] ) 怗 š‘‘š‘„ I_2 = 1/2 ∫1ā–’ć€–āˆš(5/4 怖 āˆ’(š‘„āˆ’1/2)怗^2 ) 怗 š‘‘š‘„ I_2 = 1/2 ∫1ā–’ć€–āˆš((√5/4)^2 怖 āˆ’(š‘„āˆ’1/2)怗^2 ) 怗 š‘‘š‘„ I_2 = 1/2 ((š‘„ āˆ’ 1/2)/2 √((√5/4)^2 怖 āˆ’(š‘„āˆ’1/2)怗^2 )+(√5/2)^2/2 ć€–š‘ š‘–š‘›ć€—^(āˆ’1) ((š‘„ + 1/2)/(√5/2))+ C_2 ) I_2 = 1/2 (((2š‘„ āˆ’1)/2)/2 √(5/4āˆ’[š‘„^2 +1/4āˆ’2š‘„(1/2)] ) +(5/4)/2 ć€–š‘ š‘–š‘›ć€—^(āˆ’1) (((2š‘„ āˆ’ 1)/2)/(√5/2))+ C_2 ) It is of form √(š‘Ž^2āˆ’š‘„^2 ) š‘‘š‘„=1/2 š‘„āˆš(š‘Ž^2āˆ’š‘„^2 )+š‘Ž^2/2 ć€–š‘ š‘–š‘›ć€—^(āˆ’1) š‘„/š‘Ž+ C_2 Replacing x by (x – 1/2) and a by √5/2 , we get I_2 = 1/2 ((2š‘„ āˆ’1)/4 √(5/4āˆ’[š‘„^2 +1/4 āˆ’š‘„] ) +5/8 ć€–š‘ š‘–š‘›ć€—^(āˆ’1) ((2š‘„ āˆ’ 1)/√5)+ C_2 ) I_2 " = " (2š‘„ āˆ’1)/8 √(1+š‘„+š‘„^2 ) +5/16 ć€–š‘ š‘–š‘›ć€—^(āˆ’1) ((2š‘„ āˆ’ 1)/√5)+C_3 Putting the value of I_1 and I_2 in (1) ∫1ā–’š‘„ √(1+ š‘„āˆ’š‘„^2 ) dš‘„ = (āˆ’1)/2 ∫1▒〖[1āˆ’2š‘„] √(1+š‘„āˆ’š‘„^2 )怗 š‘‘š‘„+∫1ā–’āˆš(1+š‘„āˆ’š‘„^2 ) š‘‘š‘„ = (āˆ’1)/3 怖(1+š‘„āˆ’š‘„^2)怗^(3/2) + C_1 + ((2š‘„ āˆ’1))/8 √(1+š‘„āˆ’š‘„^2 )+5/16 ć€–š‘ š‘–š‘›ć€—^(āˆ’1) ((2š‘„ āˆ’ 1)/√5)+ C_3 = (āˆ’šŸ)/šŸ‘ 怖(šŸ+š’™āˆ’š’™^šŸ)怗^(šŸ‘/šŸ) +šŸ/šŸ– (šŸš’™ āˆ’šŸ) √(šŸ+š’™āˆ’š’™^šŸ )+ šŸ“/šŸšŸ” ć€–š’”š’Šš’ć€—^(āˆ’šŸ) ((šŸš’™ āˆ’ šŸ)/āˆššŸ“)+ š‘Ŗ

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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