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CBSE Class 12 Maths 2010 Solved Paper
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Question : 22 of 29
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Find the general solution of the differential equation, x log x + y = log x OR Find the particular solution of the differential equation satisfying the given conditions: = y tan x , given that y = 1 when x = 0.
Solution:
x log x + y = log x Dividing all the terms of the equation by xlogx, we get ⇒ = This equation is in the form of a linear differential equation + Py = Q , where { = and Q = Now, I.F. = = = = log x The general solution of the given differential equation is given by y × I.F. = ∫ (Q × I.F.) dx + C ⇒ y log x = ∫ dx ⇒ y log x = 2 ∫ dx = 2 [log x × ∫ dx - ∫ dx] = 2
= 2 = 2 + C So the required general solution is y log x = (1 + log x) + C OR = y tan x ⇒ = tan x dx On integration, we get ∫ = ∫ tan x dx ⇒ log y = log (sec x) + log C ... (1) ⇒ log y = log (C sec x) ⇒ y = C sec x Now,it is given that y = 1 when x = 0 ⇒ 1 = C × sec 0 ⇒ 1 = C × 1 ∴ C = 1 Substituting C = 1 in equation (1), we get y = sec x as the required particular solution.
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