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Differential Equations

Question
CBSEENMA12033195

Solve:
      dy over dx plus straight y space cotx space equals space straight x squared space cotx space plus space 2 straight x




Solution
The given differential equation is
                  dy over dx plus straight y space cotx space equals straight x squared cotx space plus space 2 straight x
Comparing it with    dy over dx plus Py space equals space straight Q comma space space we space get comma
                   P = cot x,   straight Q space equals straight x squared space cot space straight x space plus space 2 straight x
integral straight P space dx space equals space integral cot space straight x space dx space equals space log space sinx. space straight e to the power of integral Pdx end exponent space equals space straight e to the power of log space sinx end exponent space equals space sin space straight x space
therefore   solution of differential equation is
                         straight y. space sin space straight x space equals space integral left parenthesis straight x squared space cot space straight x space plus space 2 straight x right parenthesis space sinx space dx space plus space straight c space space space space space open square brackets straight y space straight e to the power of integral Pdx end exponent space equals space integral straight Q space straight e to the power of integral straight P space dx end exponent dx plus straight c close square brackets
or              straight y. space sinx space space equals space integral left parenthesis straight x squared space cosx space plus 2 straight x space sin space straight x right parenthesis space dx space plus space straight c
or space space space straight y space sin space straight x space equals space integral space straight x squared space cosx space dx space space plus integral space 2 space straight x space sinx space dx space plus space straight c
or space space space straight y space sinx space minus straight x squared space sinx space minus space integral 2 straight x space sinx space dx space plus space integral 2 straight x space sinx space dx plus straight c
or space space space straight y space sinx space space equals space straight x squared sin space straight x space plus space straight c

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