Misc 7 - Chapter 9 Class 12 Differential Equations
Last updated at April 16, 2024 by Teachoo
Variable separation - Equation given
Example 20
Misc 13 (MCQ)
Ex 9.3, 3
Ex 9.3, 8
Example 4
Ex 9.3, 7 Important
Example 5
Ex 9.3, 6
Ex 9.3, 2
Misc 4
Example 6
Ex 9.3, 5
Ex 9.3, 14
Ex 9.3, 13
Example 7 Important
Ex 9.3, 16
Ex 9.3, 12
Ex 9.3, 11 Important
Ex 9.3, 1 Important
Ex 9.3, 15 Important
Misc 7 Important You are here
Ex 9.3, 4 Important
Ex 9.3, 9 Important
Misc 6
Ex 9.3, 10 Important
Misc 12 Important
Misc 5 Important
Variable separation - Equation given
Last updated at April 16, 2024 by Teachoo
Misc 7 Find the particular solution of the differential equation (1 + 𝑒^2𝑥) dy + (1 + 𝑦^2) ex dx = 0, given that y = 1 when x = 0. Given (1 + e2x) dy + (1 + y2)𝑒^𝑥 dx = 0 (1 + e2x) dy = −(1 + y2)𝑒^𝑥 dx 𝑑𝑦/𝑑𝑥 = (−(1 + 𝑦^2 ).𝑒^𝑥)/(1 + 𝑒2𝑥) 𝒅𝒚/(𝟏 + 𝒚)^𝟐 = (−𝒆^𝒙 𝒅𝒙)/(𝟏 + 𝒆𝟐𝒙) Integrating both sides ∫1▒𝑑𝑦/〖(1 + 𝑦)〗^2 = ∫1▒(𝑒𝑥 𝑑𝑥)/〖1 + 𝑒〗^2𝑥 Let t = ex Diff w.r.t.x 𝑑𝑡/𝑑𝑥=𝑒^𝑥 𝑑𝑡/𝑒𝑥= 𝑑𝑥 ∴ Our equation becomes ∫1▒𝑑𝑦/〖1 + 𝑦〗^2 = −∫1▒〖(𝑒𝑥 )/(1 + 𝑡^2 ) (𝑑𝑡 )/(𝑒𝑥 )〗 ∫1▒𝒅𝒚/〖𝟏 + 𝒚〗^𝟐 = −∫1▒〖(𝒅𝒕 )/(𝟏 + 𝒕^𝟐 ) 〗 tan^(−1)𝑦=−tan^(−1)𝑡+𝐶 Putting back value of t = ex 〖𝒕𝒂𝒏〗^(−𝟏)𝒚=−〖𝒕𝒂𝒏〗^(−𝟏)(𝒆^𝒙 )+𝑪 Given that y = 1 when x = 0 Put y = 1 and x = 0 in equation (2) tan^(−1)〖(1)〗=−tan^(−1)(𝒆^𝟎 )+𝐶 tan^(−1)1=−tan^(−1)𝟏+𝐶 tan^(−1)1+tan^(−1)1=𝐶 2 〖𝒕𝒂𝒏〗^(−𝟏)𝟏=𝐶 2 × 𝝅/𝟒=𝐶 2 × 𝜋/2=𝐶 C = 𝝅/𝟐. Putting value of C in (2) tan^(−1)𝑦=−tan^(−1)(𝑒^𝑥 )+𝐶 tan^(−1)𝑦=−tan^(−1)(𝑒^𝑥 )+" " 𝜋/2 〖𝒕𝒂𝒏〗^(−𝟏)𝒚+〖𝒕𝒂𝒏〗^(−𝟏)(𝒆^𝒙 )=" " 𝝅/𝟐 is the required particular solution.