If y = y(x) is the solution of the differential equation
${{dy} \over {dx}}$ + (tan x) y = sin x, $0 \le x \le {\pi \over 3}$, with y(0) = 0, then $y\left( {{\pi \over 4}} \right)$ equal to :
Solution
Integrating Factor $= {e^{\int {\tan x\,dx} }} = {e^{\ln (\sec x)}} = \sec x$<br><br>$y\sec x = \int {(\sin x)\sec x\,dx = \ln (\sec x) + C}$<br><br>$y(0) = 0 \Rightarrow C = 0$<br><br>$\therefore$ $y = \cos x\ln |\sec x|$<br><br>$$y\left( {{\pi \over 4}} \right) = {1 \over {\sqrt 2 }}\ln \left( {\sqrt 2 } \right) = {1 \over {2\sqrt 2 }}\ln 2$$
About this question
Subject: Mathematics · Chapter: Differential Equations · Topic: Order and Degree
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